It sounds like you know this but what happened is that you didn't do 4 weeks of work over 2 days, you got started on 4 weeks of work over 2 days, and now you have to finish all 4 weeks worth of work and that might take an indeterminate amount of time.

If you find a big problem in commit #20 of #40, you'll have to potentially redo the last 20 commits, which is a pain.

You seem to be gated on your review bandwidth and what you probably want to do is apply backpressure - stop generating new AI code if the code you previously generated hasn't gone through review yet, or limit yourself to say 3 PRs in review at any given time. Otherwise you're just wasting tokens on code that might get thrown out. After all, babysitting the agents is probably not 'free' for you either, even if it's easier than writing code by hand.

Of course if all this agent work is helping you identify problems and test out various designs, it's still valuable even if you end up not merging the code. But it sounds like that might not be the case?

Ideally you're still better off, you've reduced the amount of time being spent on the 'writing the PR' phase even if the 'reviewing the PR' phase is still slow.