The thing with NDEs is that anecdotal stories and reports all demonstrate a high diversity of experiences. If every single alleged NDE shared something identical--regardless of the individual's views and life circumstances (religious views, the culture they lived in, etc) that could (emphasis on could) indicate something worth investigating further.
But it appears that NDEs are all flavored by the individual's own experiences during their life, and so they see images and experiences which reflect how they experienced the world. So in a predominantly Christian society, images that reflect something nominally Christian are common. For a person with little to no experience of anything remotely Christian, they are going to experience something different.
Given the anecdotal nature of NDEs, and the deep problems of hearsay, "There once was a person who said they knew someone who had a friend who experienced X, Y, and Z"; and just how wildly different and subjective such experiences seem to be. I don't see any reason to think they are anything other than a purely subjective mental phenomenon. That NDE's are purely subjective mental phenomenon does not invalidate the existence of life after death; but neither does it demonstrate as evidence for life after death. Life after death being something untouchable by science, and remains entirely within the realm of faith.
-CryptoLutheran