All of this! Plus, I know I'm in the minority here, but to me, Steve's interest in men is most blatant in his flirting with Sam at the beginning of Cap 2 (and in the following movies). I see Steve/Bucky more in terms of epic story that defies the ages, but Steve/Sam is everyday/casual and it resonates much more with me, as in "This is real life".

ETA: Also, I like them as OT3, but I can't imagine getting polyamory in a blockbuster movie before many years.