It very definitely was not just Kol. Crowley felt just as confused by the whole thing, that somehow he was in an actual relationship and it was weirdly functional and had gone beyond just being sex. He wasn't sure how to define what it was, and he was frankly a little afraid to try, but it did help to know that Kol was just as confused.
The way Kol's words were cut off made him laugh, the sound completely muffled by his mouth over the vampire's neck, as he bit down harder, sucking against the skin. Yes, he knew that Kol's healing abilities would mean anything would fade quickly, but it still made him smug to know that even just for a moment, his vampire would be wearing his mark.
Plus, the way Kol's body arched against him made him moan with approval too, actually deciding to completely rip off the already torn shirt, because shirtless Kol was just too good to pass up. Faint drops of blood welled up under Crowley's teeth and he licked them away, relishing in the taste.