Just want to state thought that they did say specificaly that you could romance al "humanoid" companions, this leaves it slightly ambigues if maybe there is a synth companion among them or not. Cant remember them saying "human" companion anywhere, but i could be wrong.
PS: this is not a reply to anyone's statement btw, just saying what i think i heard and how its dubious in a way as to not confirming nor denying it to be posible.