Hello, Lost
Based on my personal experience, I have met only one person who pretended. I had known her on a forum back in 2002, and this happened after she spent one week at a very famous Institute. Up to that day, she had been a nice, kind, spiritual person. Then she had this one-week experience during which she said they were completely isolated from the outside world and constantly immersed in brainwave entrainment sounds, even when asleep. Maybe this is a beneficial experience for most. But she was obviously different and the experience caused her undeniable mental damage.
She started by saying that during that week she had remembered an NDE at an age around 5 or 6, when her cousin had killed her, and a new soul had walked-in, which is why she had no memories of her life until then. She shortly created a very heavy atmosphere on that forum until the day she and her followers left, and created a new forum.
On the new forum she described all her previous lives (dozens) some of which where analyses by experts and regarded as a mere invention. A few years later, I accidentally came across her story on another site, and she had represented her NDE in a completely different way, as happening on a bus.
This is why I have come to believe that a full immersion in brain entrainment sounds for a whole week (this is how she described it anyway) can be dangerous for a mentally unstable person.
On the other hand, I have come across so many genuine NDE accounts and find that experiencers can find it very difficult to share other-worldly experiences with human words. Some of the experiencers need help to get used to this earthly world afterwards, others (as in the case of Betty Eady) experience depression from the Home-sickness resulting from an NDE. Not all NDEs are instantly remembered: this is true. The memory may come back gradually.