That's interesting hypothesis but it doesn't fit well with what people after NDEs actually say. They don't talk about some blurred vision but a sharp, very concrete but hard to describe experience. And some of them talked to Jesus/angels/whoever they think they saw. They remember it well. Watch some interviews on YT, Howard Storm is an interesting example.
People will be judged according to what they were given. How about those who saw Jesus, heard Him speaking and saw His deeds? Not much room for faith there. Yet still Judas betrayed. Even Apostles still had to make choices, follow what they thought was good and, as human beings, made many mistakes. Being convinced what's right and what's wrong doesn't make your life an easy walk.