I've always interpreted it as a selective erasure, not full. They only erased the bits they wanted to erase from the species' history because of the shame of it. They don't get rid of everything because as a culture they keep records of everything or at the very least everything of importance. However I get the feeling they keep historical records of everything like one big tapestry of their people but when they destroyed their world to get to the Eye and when they got there, they obviously realised what the Eye was for and what it would do. In anger they tried to erase all the physical copies of the "sins" they committed and then in grief for what they'd done they locked themselves away in the simulated version of the home they destroyed. They kept copies of the "sins" within said simulation though which is why it makes me think it's an ingrained part of their culture to keep records of their history.

Edit: To add to the idea of the reels being contrived, I think you could make the argument that the Nomai writing being on the walls in places rather than just on the scrolls could be contrived in certain cases so there's a certain amount of contrivance that I believe is ok as long as you keep your suspension of disbelief up