But to determine its merit a maintainer must first donate their time and read through the PR.

LLMs reduce the effort to create a plausible PR down to virtually zero. Requiring a human to write the code is a good indicator that A. the PR has at least some technical merit and B. the human cares enough about the code to bother writing a PR in the first place.

It's absolutely possible to use an LLM to generate code, carefully review, iterate and test it and produce something that works and is maintainable.

The vast majority of of LLM generated code that gets submitted in PRs on public GitHub projects is not that - see the examples they gave.

Reviewing all of that code on its merits alone in order to dismiss it would take an inordinate amount of time and effort that would be much better spent improving the project. The alternative is a blanket LLM generated code ban, which is a lot less effort to enforce because it doesn't involve needing to read piles and piles of nonsense.

I think most people are in complete agreement.

What people don't like about LLM PRs is typically:

a. The person proposing the PR usually lacks adequate context and so it makes communication and feedback, which are essential, difficult if not impossible. They cannot even explain the reasoning behind the changes they are proposing, b. The volume/scale is often unreasonable for human reviewed to contend with. c. The PR may not be in response to an issue but just the realization of some "idea" the author or LLM had, making it even harder to contextualize. d. The cost asymmetry, generally speaking is highly unfavorable to the maintainers.

At the moment, it's just that LLM driven PRs have these qualities so frequently that people use LLM bans as a shorthand since writing out a lengthy policy redescrbiing the basic tenets of participation in software development is tedious and shouldn't be necessary, but here we are, in 2025 when everyone has seemingly decided to abandon those principles in favor of lazyily generating endless reams of pointless code just because they can.