Demanding evidence and support for affirmative claims regarding a personal, subjective experience is possible and not at all unrealistic. If a person makes a claim, they should be able to support that claim or recognize that it is just their personal opinion based on bias, desire, and willingness to believe. It certainly is not based on objective evidence that can be shared. The unrealistic and impossible are in the attempt to provide that evidence.
Do you believe every opinion that any person tells you? Why not? Do you accept any claim any person makes based on their subjective experience? Why not?
If you believe NDE's are a spiritual experience and meet someone that claims they are evidence for the existence of aliens since they are the result of advanced alien technology. Do you ignore their claim? Do you ask for evidence to support the claim? Do you accept it and try to reconcile it with what you already believe?
Others on here have attempted to provide what they have mistaken for evidence for the spiritual nature of NDE's. While it is not evidence showing what they claim, they made an attempt to provide evidence. Why do you think they did that?
You can believe what you want, but coming on an internet forum making claims about something, even a subjective experience, requires support or the claims can be dismissed without comment.
Beyond that, I am not sure what you are trying to say. Claiming that NDE's are spiritual events that reveal the existence of life after death requires evidence to support the claim.