May be a bit of both, but i do have a very selective memory.. Some points to give you examples
1) I can choose to erase something from my memory. I can decide I dont want to remember something, erase it, then if at a later point I try to remember it I can not. I have the memory of doing this many times but cant remember what exactly it was I was choosing to forget any of those times.
2) I learned at a young age i had to optimize my mind for efficiency if i wanted to accomplish great mental feats because my brain was not any more intelligent than an average brain. So I had to hyper optimize. As such I exploited #1 and made it a point from a young age to only remember the conceptual understanding of an idea needed to recreate the idea, but not the arbitrary constant values needed, which could always be looked up. This results in things like phone numbers and names, and other points of data not entering my head at all while the understanding of the ideas get preserved well. This was super powerful in math because i could just derive any equation i needed for anything and reconstruct ideas without needing to memorize the formula or numbers.
Also, yes to the other point I am **extremely** over stretching myself. But that is intentional and stems from work but also into my personal life. Basically in most of what I do im the only person who can manage the team since i am usually the only top-expert they can afford (I usually cost a company something like 500K to a million for 3 months worth of work). Which means I need to spread my talents across a very wide swath and fill in even the most rivial things with other people and letting me give the absolute minimum needed to convey my knowledge to the team to unblock them. This results in an intentional overstretched interaction where I am intentionally spread quite thing to best utilize my talents.
This is also why you see so many typos, I type very very quickly and have no time to edit or proof read what I say as I am trying to cover as wide a swatch as I can.