I think the others merely assumed it was a joke, not so much him intentionally doing it to be cruel.
Though, I will say this... My initial plan was to do a longer piece. In that one, Remus would have originally been out to woo Severus secretly. But, when his friend found out, he'd have to play it off as him setting up Severus for a big prank. And then continue with it...as in, feel as though now he has to continue the wooing, but while knowing that the ending is far from what he'd want. I thought that might be a little too cruel, though, to the both of them.