It's interesting to me you don't see the logical fallacies necessary/inherent in that approach. Obviously skepticism is warranted, but to dismiss in that it *must* be explainable through some [known] other phenomena is no more or less intellectual than to assume I made contact with the Afterlife.
It's interesting that you caveat the limitation of encounter to "severely limited", which is neatly ambiguous and subjective. Many of our daily experiences are severely limited or individual, yet no one questions us if we recount the majority of these events, even though nearly (or in fact) everything is impossible to verify given the arguments/understanding about perception and memory. To appeal to the fact that many of these are "common" fails on two points:
1. An appeal to majority/tradition.
2. If our experiences/memories are highly undependable, then no matter how many experience something, it is no more or less worthy of consideration, whether experienced communally or in isolated cases.
Edit: TBC on skepticism, the last thing I should expect is for someone to come away from this discussion with the opinion that "Well goshgolly, Overwatch says he saw an apparition once so they must exist." But there's a difference between skepticism and outright rejection.