AI assistants are also quite good at helping you create a high level map of a codebase. They are able to traverse the whole project structure and functionality and explain to you how things are organized and what responsibilities are. I just went back to an old project (didn't remember much about it) and used Cursor to make a small bug fix and it helped me get it done in no time. I used it to identify where the issue might be based on logs and then elaborate on potential causes before then suggesting a solution and implementing it. It's the ultimate pair programmer setup.
Do you ever verify those explanations, though? Because I occasionally try having an LLM summarise an article or document I just read, and it's almost always wrong. I have my doubts that they would fare much better in "understanding" an entire codebase.
My constant suspicion is that most results people are so impressed with were just never validated.