I started just reading this thread to see people's opinions. I know they differ to mine but still wonder what goes through people's heads sometimes. More of an interest to understand humanity than anything. I have a personal opinion that everyone is bisexual, or more that sexuality is a sliding scale. Even a straight guy can admit when guy is good looking but might not consider a relationship with them.
In the scenario you put forward, if I'm attracted to them already, they identify as a girl, just they lack the last operation to confirm it, then there would not no reason to stop the relationship. They are a girl as far as looks and personality dictate.
However I would have an issue with the dishonesty.
Hmm, pie.