I assume the policy was written by rational, reasonable people, with a practical goal in mind: to prevent "AI slop", that is, dubious-quality, high-volume contributions by people who don't exactly understand how their PR works, and how the project works, but "computer says yes" because tests (which they also do not understand well) seem to pass.

If a submission (PR, bug report) is high-quality, and the person behind it is responsive and clueful, so that the useful parts of the submission can be taken, and problematic parts, fixed, then it does not matter what process has produced the code. It could as well be a Boltzmann brain [1].

Given that the author of the contribution actually got a grip on the problem, and on the solution, the limitation of "no AI use" is no longer load-bearing. Not only might it have been counterproductive — it's also unverifiable in practice. It becomes absurd, akin to a demand that the text must have been edited by Vim and not VSCode. It must be noted that a misguided policy may indeed force the contributor to delve in the depths of the process of PR creation, and showcase every manually undertaken step in an attempt to prove that no AI was involved. Ironically, it is no secret that many less scrupulous participants might leverage AI to imitate just that. It must be noted though that the decision ultimately belongs to the project maintainers.

(The above paragraph was hand-crafted for your and my entertainment.)

In short: by default I respect the authors of the policy and hence assume that they enact the policy for reasons that are rational, not religious.

[1]: https://en.wikipedia.org/wiki/Boltzmann_brain

Without a policy, I refuse to have a clear understanding!