That's true, those who have NDEs are not fully dead, and even if they were dead for a given amount of time, they were not dead long enough to cross over to the spiritual world. If they had crossed over they would not have been able to be revived.
Nobody knows what happens when a person actually crosses over to the spiritual world since that has never been revealed in any scriptures. There are some books about the afterlife but spirits who were communicated to my mediums always say that the spiritual world is too different from this world to be described such that we could understand, which is what Baha'u'llah wrote.
I know I've told these stories before, but I thought I'd share them again in response to your post.
I don't know anyone who has had a near-death experience, and I haven't either. I have, however, seen a person's spirit briefly leave their body and then return shortly after. I've seen this occur more than once while I've been in hospitals and nursing homes. I was present when my maternal grandmother passed away in the nursing home, and I saw her spirit leave her body moments after she died. I never told her while she was alive that I'm a psychic medium and I can communicate with the dead. So, she was astonished and perplexed to learn that I could see and communicate with her now that she was a spirit. She had confided in me before she died that she was at peace about dying, and she reassured me again in spirit. She told me that she could see a light and she could see my grandfather standing in the light. I told her that she should go see him, and she did. She crossed over peacefully. I was also present when my grandfather (her husband) died, and his reaction to my being able to see and communicate with him in spirit was the same as my grandmother's reaction. Not only was I present at their death and I communicated with them in spirit, I was also aware of their impending death before they died. And that wasn't the first time I knew when a relative had died, and I wasn't there to see it. I sensed when my husband's grandparents had passed away. I told my husband at the time, but I didn't tell anyone else in his family.
My maternal great-grandfather was very sick and died when I was 12 years old. I saw him shortly after he died. He died at home in his bed, surrounded by several loved ones. At the time of his death, I was staying with my paternal grandparents in the next town over. It was late and I was in bed. I suddenly woke up and my great-grandfather was standing in front of my bed, smiling at me. I got out of bed and went into the living room to tell my grandparents that my great-grandfather had passed away. They didn't know what to say at first and just gazed at me. My grandmother told me that I had been dreaming, and she told me to go back to bed. So, I did as she said and went back to bed. I sat up in bed and just watched my great-grandfather. He was sitting on the edge of my bed when I came back into the room. We didn't say anything to each other. I didn't know what to say anyway. We just stared at one another. I looked at the clock on the nightstand when I left the room to tell my grandparents that my great-grandfather had died. It was 9:15 PM.
I heard the phone ring about fifteen minutes after I returned to the bedroom. I heard my grandmother answer the phone and I could hear my aunt on the other line. My aunt has always talked in a loud voice because she is hard of hearing. My aunt called to tell my grandmother that my great-grandfather had passed away approximately 15 minutes earlier, and my aunt asked my grandmother to tell me in the morning. The bedroom I was in was right off of the living room, so I could hear the entire conversation. I got up and tip-toed to the door and peeked out through the crack in the door. I saw the look of shock on both of my grandparents' faces. I heard my grandmother whisper to my grandfather, "How did [my name] know that he passed away when she wasn't there?" My grandfather just shook his head and whispered back, "I don't know." I never heard either one of them mention what happened ever again.
My paternal grandmother passed away in June 2010, when I was 37 years old. She had passed away a couple of days after I saw her last in the nursing home. I knew that she had died when my uncle called to tell me and my husband. My husband and I attended her funeral at the church where she had been a long-time member. As I entered the sanctuary, I noticed my grandmother standing behind her coffin, looking around at her family and friends, as well as the other people who were already seated. As she was looking around, her eyes met mine and she smiled. I smiled back at her and went to sit down with my husband. He leaned over to me and whispered in my ear, "You can see her, can't you?" I nodded yes. I didn't speak to my grandmother until we were at the cemetery for the burial. I was concerned for her because she hadn't crossed over yet. After the service was over and everyone else was standing around talking, I caught my grandmother's eye and nodded to indicate to her that she should follow me. I walked quite a distance away and stood behind a tree so that I could speak with her without drawing any attention from the other people at the funeral.
Before I could say a word to her, she looked at me and quietly said, "I knew it." and I understood what she meant. She apologized for not talking to me about my psychic abilities earlier in my life, and she said that she regretted not intervening on my behalf when she knew about what I was going through at home. She said that she needed to explain herself, and I listened to her explanation. She asked me to forgive her, and I told her I had, which was the truth. I wanted her to be at peace so that she could crossover and not be stuck as an earthbound spirit. We spoke for a couple of more minutes, and then she crossed over. I haven't seen her spirit since.
Personally, I think that is unfair of God not to tell us more about the spiritual world, especially for believers who have to believe and have faith, putting all their eggs in one basket.
I've also spoken about my personal experiences as a psychic medium and how I've asked several human spirits about God, and the responses I received were either "Yes, God exists" or "No, God does not exist" or something to that effect. However, other spirits seemed confused about whether God existed or not, as well as whether heaven even existed, because they weren't in heaven yet and hadn't seen God, despite their belief that they would be with God in heaven after they died. Despite my efforts to uncover the truth, I've never received a definitive answer as to whether God is real or not. I have, however, had the impression that asking a question about whether God exists or not might be considered taboo because the question wasn't always well received when I asked. Some spirits I asked refused to answer questions about God or Jesus. They were either apprehensive to answer or were angry that I asked.
On the other hand, I've spoken with some earthbound human spirits who asked me questions like, "Where is God?" or "Why am I not in heaven yet?" About six years ago, I was involved in a paranormal investigation at the Hotel Galvez & Spa (in Galveston, Texas) with some paranormal investigators whom I personally knew. As we were walking down the hallway of the fourth floor with our spirit box turned on, we heard a spirit say, "Where is Jesus?" and another spirit anxiously say, "The children aren't in heaven yet!" One of the investigators suggested that these spirits may have been responding to my presence, but we didn't get any answers from either of these spirits when we asked them questions, such as if we could help them cross over. It's because of these experiences and many others that I no longer believe that human spirits either go to heaven or hell in the afterlife and are then eternally trapped there.
