That's an interesting take I don't see anyone else bringing up.

It would also, I would think, make it easier for the 30% fewer engineers to earn a better living in the long run and reduce human management effort.

This makes the most sense to me. So far AI, being fallible, can only augment humans so you can have less humans to do the same work (or tasks where accuracy can be less than 100%, like lower level support calls/questions). Next comes the task of re-balancing the distribution of labor or teaching other departments to utilize AI.

To me that rings the most true because where AI saves me the most time is in never having a bug that takes more than a few hours to pinpoint, even if I'm looking in the wrong place, because with enough clues the AI will look in the right place before I think of doing so. Like finding a needle in a haystack. It doesn't suddenly make me 100x more productive, but it saves a lot of time on some time consuming tasks.