Likely because at this point, it's an almost impossible standard to hold for an open source project.

"AI code" is a very vague term. What if somebody used an LLM autocomplete in their IDE? What if they used an LLM to summarize and parse documentation, but wrote all the code themself? What if they generated the initial code with an LLM, but then heavily modified and tuned it by hand? What if they wrote the initial code by hand, but used an LLM to debug or optimize it? What if they wrote all the code by themself, but used an LLM to write unit tests and modify documentation?

If you're against every single example I gave, that's fine, but many if not most of these would be nearly impossible to tell if somebody had done it. Project maintainers are already spread extremely thin without also having to be AI detectives. Many/most large projects have already banned AI slop contributions, but that only stops the most obvious and lowest quality vibe coders and agentic bot spam.

The truth is that a large portion of devs are using LLMs in the kinds of ways I described earlier, right, wrong, or otherwise. Some distros are leaning into the hype, others are just quietly doing their own thing.

If you want to steer clear of explicit AI inclusion, I would just stick with distros that aren't bragging about implimenting those kinds of features. Check their main project page, check their official blog if they have one, look at the lead maintainers' github/lab pages and projects and see if they are big into AI stuff or not.

At this point, that's probably the best you can do.