I think one would be hard-pressed to come to that conclusion for all situations. Certainly one can fabricate feelings but when one experiences His presence and virtue (power) flows and someone is healed, it would be difficult to convince that person that what they felt, what happened to the person who received the healing power, was all a fabrication.They just convince themselves of that thinking it's something really there.
Obviously having a feeling of presence is not something unusual , as people have those type of feelings all the time for just about anything they are focusing on in their minds.
I think it comes from our predator/ prey intuition that are ancestors had to rely on to stay alert. That also applies to perceived protectors like guardian angels and spirits and stuff like that to conversely have a sense of security and well-being.