You can’t be upset because they want to know the truth, seriously. When a project has concerns about generated code, it is for a reason.
"This looks like AI, closed". And you as a new IC with no connections, no community visibility have no recourse to fight back against it. Anti-ai people love boasting about humans > systems and forget about those humans that will surely be negatively affected by this, even if low number.
If you are a new programmer who is just learning and spend time creating a PR for a project you have a lot of respect for and the first interaction is someone falsely accuses you of using LLM's then closes your PR you've now removed someone who could have genuinely grown into your community from ever joining.
Not only that but since now you are by default a suspect of having used an LLM (and you need to prove you didn't use one) why even bother not using one? You are going to get accused of it either way.
Are there some potential contributors who might be discouraged because of this policy? Probably. Will maintainers have less time wasted by obvious low effort changes and engagement? Also probably. A user of AI is, in the experience of many maintainers, way more likely to be lazy than engaged.