To me, AI is just a tool that helps you work on text. Person who uses it still has the final say on what is being submitted. Thus, just like nobody cares about texts being processed with other tools — spellcheckers, text processors, XMP beautifiers, etc. —nobody should care about how the text was produced, even if LLM generated the entire section (in fact, the last 4 words were generated by Gmail's auto-suggestion to use active voice, and it replaced my previous phrasing).

So, i my opinion, the best course is to ignore capabilities of modern models and just let the submitters be responsible for what they authored in whatever way they like. Also, I don't think that LLM involvement can be reliably proved anyway, so ....