The issue is with how they define minors. Considering they're stylised cartoons it can be pretty subjective, and for some, simply having a flat chest = child, regardless of anything else. In other cases, curvy body + large breasts can also be considered child if they are deemed 'too cute', etc.

It leads to inconsistency, which leads to people creating content that is well within the guidelines deciding to not publish to Patreon as they can't guarantee whoever is enforcing the rules that day won't arbitrarily decide otherwise.