>>531801193
Because the point was that Ayin couldn't handle the loops due to how much mental damage it caused him, so he opted to get mind wiped, and slowly introduced to how fucked up everything is in there to maybe get used to it, and then fed back his own memories through the course of days to maybe try and not break down and sob about the situation and commit suicide one more time over it.
They probably tried keeping his memories intact before and it just inevitably lead to a breakdown if left as is for too long, so she had to pretend he was just a random in order to keep up the charade for a while.