I don't have experience with the stacked PR workflow and often find myself asking the same questions you are.

As far as I can tell, the biggest benefit of stacked PRs over just making a coherent series of commits, is that it might make it easier to start work on your second PR before you merge the first one?

With human-in-the-loop coding, that sounds like it could lead to a lot of wasted work if the first PR gets substantial feedback. But with agentic coding, I can imagine how it might be desirable to keep the agent chugging while the first PR is under review.

Interested in learning more about it and generally agree that AI is stressing the current review paradigms a lot of us are accustomed to.