There is absolutely no need for stopping estrogen and antiandrogen administration for this kind of surgery, or FFS (SRS is a very different story, there are much more risks involved). The possible risks, for someone who is overall healthy and has coagulation factors in normal ranges, are so small, that it doesn't make any sense. IF anesthesiologist is capable enough to follow what is happening, knows how to read possible complication signs, and use prevention just in case if needed, there is no need to stopping HRT before surgery, other than it being surgeons demand to avoid any possible complications and related consequences like financial compensation and legal costs, while the only real cost here is patients well-being and hormonal disrupt for no good reason. You don't have to stop with HRT, but be aware that surgeon have every right to not perform you surgery if you didn't follow his/her instructions.