I scheduled a 'chat' with our company nurse and told her what I was up to. There is a level of confidentiality there, so I was comfortable telling her I was in the process of transition and one of the steps I was taking was gender affirming surgery. I never told her exactly what was being done. My Dr. is Brassard (in less than 3 weeks...w00t!) in Montreal, CA. If you have read any of my posts about paperwork with their front office, you will understand why I skipped them entirely getting my FMLA paperwork completed. I went straight to my primary care Dr. since she is the doc I am going to follow up with regularly after the surgery (and I did warn her well in advance of my need for her to fill out the paperwork for FMLA, to which she happily agreed). She also filled out the paperwork for my wife to get her FMLA since she is my caregiver for a month post-op. So, she filled out the paperwork dating my eligible and needed time of 2 months starting with my surg. date, and she and my HR told me that as a caveat, should I need more time, I just need her to send another letter stating I need more time, since FMLA allows you 12 weeks in a calendar year.
Mind you, I have been very much in touch with my HR dept and the nurse about my process. YMMV. I am burning vac time, sick time, pers. time, and using short term disability (some at 100% pay, and some at 60%) to cover my time off, and still may go a week or so without pay depending on how I feel and how I am healing (btw, my company sucks at allotting leave time ...ugh!).
Hope this helps!