"And confusing," Cas can't help but agree with that. Emotions are strange to him, always has been. That makes the most sense if any excuse he's been given so far.
"So long as you're happy," he finishes lamely -- and it's not so much a statement as it is a question. Is Q happy? Because Castiel doesn't understand at all why if two people are clearly so find of each other why they aren't together.