I think what it means is "we will judge you based on the code you submit, we don't care if it comes from an AI". Also probably "we will judge you if you obviously don't understand the code you submit".

At least that's how I do it. When someone offers a patch to an open source project, I don't really care if that person has a PhD, or if that person does this in their free time, or if that patch is actually the result of a whole team working together. I judge the patch based on the value it brings to me as a maintainer.

Obviously the code has to be good, but also the interaction with whoever offers the patch has to be smooth: if I have a question, if I need them to confirm/change/test/elaborate on something, I need that to work.

If I feel like I would be faster doing the work myself AND this author is not putting effort into it (e.g. they just copy-paste an AI), I will not review that work. Possibly I will distrust that author. If too many contributions end up wasting my time, I will start limiting the contributions to people I know/trust, etc.

In terms of maintenance, I don't see a difference between getting a contribution from a stranger or from a stranger using an AI.

In terms of philosophy, that's obviously different: One may not want to accept contributions from people using AI because they think that AI is bad for society, for instance. And I would totally understand that. But if the stance (and it seems to be Linus' stance) is that a patch is only judged based on its technical merit, then I don't see why AI-in-the-loop would be an issue.