Yes, you really should disclose everything that may be medically relevant.
For example, dosages for anesthesia are different for a GG than a GM. Depending on how long you may have been on HRT, your body may react differently and it all should be taken into account.
When you are under general anesthesia, you are closer to death than any other time. Your respiration is halted and must be constantly observed by the anesthesiologist. This is only one aspect. The Health Information Privacy Act of 1999 (HIPA) forbids any disclosure of medical information by *any* medical staff under penalty of civil and criminal prosecution. Your information is private and anything you disclosure to them is to protect your life. They may not approve of you as a MTF, then pass on them and search elsewhere. But any information you may give them in the process of consultation is PRIVATE.
Additionally there is a large difference between the thorax (chest) of a male and a thorax of a female. He (I assume your surgeon is male, sorry if I'm wrong) may get the impression you are male just from that. Placement and size of implants are different for these size thoraxes. If you are looking for a pleasing shape that will definitely be a factor. Also, many MTF's have broad shoulders and the placement of the BA's will be such that you may have a large cup size but no cleavage. Welcome to my world. The only way I can get any cleavage is to duct tape the cups of my bra together.
Check out your surgeons background. If he has a website, be sure that he is a member of the American Society of Plastic Surgeons (ASPS) or other relevant group.
And to answer your question, yes, my surgeon was completely aware of my MTF status. He also performed my facial feminization. He was Dr. Zukowski. I am a proud "Z" girl. Feel free to PM me. Check out my blog "Sandy's Transition" for my surgery experience.
-Sandy