Two problems: that kind of documentation often does not exist, and if it does, that kind of documentation often gets ignored. "Too theoretical, not practical, etc. etc., but more often if they were self aware and being honest, it's more like 'I don't understand'"
I mean, I agree, this kind of documentation can be invaluable, if employers are willing to let (and encourage) engineers to write *and* read it. (What did you do today? Read a bunch of documentation that you barely understand? Do better tomorrow!)
Concurrency poses a real challenge, as most programmers don't even begin to comprehend the issues in play. I know I was taking graduate classes before that light bulb really turned on.