Because, as the FAQ section clearly states, the technical and management aspects are not the only ones. There are also legal issues, and until they are clarified or resolved it's best not to let code in that has the potential of causing a legal issue.

I suspect one of the principle reasons for the blanket decline is specifically that AI generated PRs are already responsible for a substantial uptick in the amount of work required to be done by maintainers. Engaging in discussions about those PRs may be more fulfilling and useful for the developer but it also then increases that work yet again manifold, so that would likely be highly counter-productive.

What I don't understand is: if you, for example, are a heavily AI-using dev, who spots a problem in OpenJDK, and you use Claude to figure it out: ok, why can't you then write the solution and PR yourself? Write your own code to replicate the functionality that Claude did, in your own style. Have Claude explain why this fixes the issue (it probably already did) and test it. If it works, write your own explanation and submit it as a PR.

I've done this a handful of times for smaller projects, in languages I'm unfamiliar with. Nobody complained because I didn't just copy the shit out of Claude, paste, copy the explanation, paste, and make a PR. I used Claude to increase my understanding, if even a bit and in a necessarily incomplete way, and did it myself.

The interim policy you're proposing seems to have far different priors. The clearest indication of their stance is that they don't even want bug reports that have AI generate part of the text. You don't take a stand like that (imo) unless you've experienced some serious AI-related burnout.