Good point, if for example Hindu's have had the same kind of NDE's. Their conception of God is very different. In fact, I don't think there's is no heaven in Hinduism. I don't think Nirvana is equivalent to heaven, i.e. a distinct place where God is that you (may) go to when you die.
Having said that, I don't know about this guy's and other NDE's. There's nothing Biblical about being able to be saved once you're dead.