I agree about the "explicit" definition. I get confused all the time and had discussions on another thread about it. Everyone has an opinion of what they consider "explicit". So I think more specific details should be used.
For me, explicit nude means you see the full vagina. Between her legs. Not full frontal. Full frontal is too common. In my opinion it should be labeled "Explicit female nudity". Or if a male shows his penis, "explicit male nudity" if it's both "explicit male and female nudity". Otherwise, we're left thinking we'll either see this or we'll wonder if the sex is real.
Explicit sex should be real/unsimulated. In my opinion, not two people touching privates. That's also common to an extent. So people should say "explicit sex unsimulated". If we want to consider simulated nude sex scenes to be labeled explicit, then say "Nude simulated sex".
These are just some examples. I don't think it's difficult to add extra words just so some of us don't get confused. You guys have no idea how I'll watch a sex scene posted, called explicit, with people claiming it to be good. But when I watch the scene, it looks like unsimulated sex, but theres no clear evidence. So I'm stuck wondering.