I don't have the answer here.
I just know, that if I would point a average human to a messy old codebase, he or she would just shrug helplessly. Even most programmers.
But if I tell claude to start digging in, refactor, update outdated tools .. it produces results. So there is some "understanding" I don't know how else to call it. So surely it is not a general intelligence, but it is certainly useful.