It's actually refreshing behavior from Castiel. Away from his family, away from the watchful eyes of his uncle and cousins, Sam thinks he's getting a better look at the real Castiel. And yes, he's finding he likes it very much.

He bends, leaning down to press a kiss to the long line of neck that Castiel is showing. "We will," he agrees as he pulls away. "Though not until tomorrow night, after we're married." Sam pauses, then sighs. "I'm sorry that...it's not going to be a very big wedding. On such short notice, it'll mostly be a justice of the peace and the pack. I mean, we've had things planned as much as possible and there's a really lovely grove on the grounds..."

But it wasn't anything like what Castiel would be used to. He's marrying far below his family's wealth, after all.