I think he’s just “no homo”ing on Dean’s behalf

personally I think he doesn’t know Dean’s bi (or at least isn’t convinced of it - so what we see is all the fault of the directors and stage manager-type people), but he does know Dean’s in love with Cas. and he plays Dean as in love with Cas (and l i e s when he tells us otherwise). and he’s probably confused by the fact the writers are so inconsistent with their “Dean likes girls. oops, Dean likes this boy. oh yup, girls again” (then again, I could be underestimating his knowledge of sexuality things? with Misha as a friend I’m sure he’s had bisexuality explained to him)

the way I see it, when Jensen talks about Dean and girls he’s not discarding the possibility of Dean being in love with Cas, but he’s sort of tiptoeing around the fact of it with white lies and carefully missed-out references to people other than women.

so when he says “falls in love with a woman” I’ll happily believe he actually means to add a silent “or whatever” on the end, so as to be inclusive of multidimensional wavelengths of celestial intent.

(of course I could be wrong, and Jensen actually thinks Dean is straight. if that’s the case, he has noooo idea how bad he has it for Misha.)