He doesn't believe him this second but...he wants to believe him. And he trusts that Corbin wouldn't lie to him or even just try to tell him what he wants to hear, mostly. So. He's going to trust Corbin, and he'll believe it eventually.

"You'd better." Harry smirks, but there's a softness ot it. Hell yeah unexpected snuggles. He won't even hook him if he does it.