Finn isn't a virgin. In fact, he was the biggest slut in his squadron. He knows what sex is, he knows what he likes, and he knows how to throw himself at Stormtroopers.

Poe isn't a virgin, but he might as well be one. He's spent so much time Devoted To the Cause that he's barely had a relationship in ten years, and he's such a sweetheart that nobody can get him in bed without six months of dating and flowers.

Finn throws himself at Poe pretty damn hard.