Expedition: general discussions.

Yes. He doesn't know how to make himself likable; people don't accept arguments, no matter how reasonable they may be. If he's downtrodden, poorly dressed, and unable to carry himself with confidence, a loner who also smells bad, it's unlikely anyone will listen to him...

In the case of two equally foul-smelling loners, people will obviously listen more to the one who possesses better formal logic than a savage from the forest. That is, in such a case, the difference in intelligence can be taken into account.
But what if we have two people, and one looks and speaks slightly better, while the second is noticeably better and argues without logical flaws?
No, of course, if we're talking about checking some kind of charm or allure, then intuition can be compared with charisma and physical attractiveness and not taken into account, but in the case of persuasion, I completely disagree.

And what makes you think that intelligence will be a stat?

Interesting... Well, even if it isn't, I'm more talking about the situation in general. And besides, if intelligence is absent, it's probably more difficult to make a substitute check for charisma.