> I wonder if a similar thing can happen with non-physical pursuits (specifically, coding) if relentlessly forced to over-do one thing over a long period of time.

I've seen this happen to other people and mildly had it happen to me, so yeah I'm convinced it's a thing. I'm probably back to 80-85% of what I was, but it's been almost 10 years, so age (I'm now 40) has maybe made that my new ceiling.

> ...experience

Even though my raw LOC has declined, I'm a much better engineer than I was 10 years ago. I credit being better able to avoid big bads and pick probable right answers because of experience. I've focused on being a better systems thinker rather than like, nailing algorithms and such, and I think that's been an important part of my recovery: one using other parts of my brain and finding something else to be interested in, and two broadening my thinking.