Confused about over correctors

Hello, I finished my Invisalign treatment, and went on to a retainer. However I'm a little confused because I had 18 aligners, and 16-18 said "Over Correction" with a + and made my teeth pretty crooked after they had become straight, and I wore those for much longer than the regular correctors. My assumption is that the over correctors are designed to push the teeth even further past being straight because teeth shift back over time. So I asked my dentist, and at first it seemed like she didn't even know what I was talking about. So I told her my assumption about them and she agreed (a little disconcerting that she couldn't explain it herself). So that day it was time to get impressions for my retainer. I asked her how it makes sense to get a retainer based on the now crooked impressions. She said over time they will shift back and I believed her and left. But then I thought, how can they shift back over time if every single night I am locking them in that position, which is crooked from the over correctors? I guess at this point I don't believe that it's true, and I think that maybe my dentist doesn't know what she is doing. I also had a thought, that maybe they do this because they know people are generally bad about wearing retainers, and it will eventually shift back over time without the retainer. But my teeth just seem to stay exactly how they left off, and I have not even been wearing my retainer in the last couple of months, because I feel confused and I wanted to see if they started to shift back, but they have not really. If someone could explain to me how this really works I would really appreciate it.