It's true that Castiel has always been a curious creature, it's in his nature, something he will never be entirely rid of. He's inquisitive, and while he might be passive, he is not easily frightened or intimidated. This beast before him certainly does not appear innocent, and it's clear enough in his father's imprisonment that it is capable of cruelty, and yet there is an intelligence in its rough voice that has him giving pause, that makes him think that perhaps there is more to this creature than meets the eye. Since being flung against the wall by his throat, he has not been threatened, and he might be imprisoned, but.. he does not feel as if he is in any immediate danger, so he's not really hesitating from this creature, or drawing back. As of yet, he sees little enough reason to.

But even if he isn't afraid, he's still angry, still distant and cold, and he doesn't pursue his line of questioning any longer. For the moment, he's too aggravated to really care about this creature's name or identity past a brief question, so he does not probe any deeper, only seals his mouth closed and looks away, silent.