Sorry. I think the direction of the one-way Dean/Castiel went over my head. I interpreted the direction as Castiel -> Dean, and Sam's answer as intentionally ambiguous: it isn't his vessel's sex that's the determinant, but Sam isn't saying what he guesses, which is that Dean doesn't see Castiel that way. And if Sam's that ambiguous, it's because telling an angel he hasn't got a chance is going to hurt. But Sam's chosen to hurt innocent things before, so perhaps breaking an angel's heart is something he deserves to have to do.

Yeah, if I have to take a paragraph to explain it, and I may have been exactly wrong anyway... sorry.