AFAIK, there is no correlation with T use in transmen and DVT. Not in anything that I've read. What I would do is email one of the larger LGBTQ clinics that provide HRT (Whitman Walker, Callen Lorde, Mazzoni, etc.) and see if they could foward you a FTM HRT information sheet to provide to your endo. I don't have mine anymore, but it listed out all the potential risks, effects, benefits, etc. on there. Literally anything that could possibly happen to you was covered, so it would be a good reference sheet for him to have.
T can cause elevated RBC anytime. What most guys do if theirs is high is donate blood. That'll drop it down. But yes to the increased bleeding risk with surgeries, especially long ones. Some surgeons doing top surgery don't care because it's a relatively quick procedure. Same with the hysterectomy. Some do care though, and would want you to stop. I *believe* all the major surgeons doing bottom surgeries in the US want you to stop prior to that, because those are typically much longer procedures. Top surgeries are usually 2-3 hours, where bottom surgery can be 6+ hours without complications during the procedure.
Looking at what KarinMcD just posted, it looks like T may help your case, especially if you're near your ideal body weight or otherwise have low body fat. T is converted to estrogen in fat cells, so if you're relatively fit or getting there, it seems like T would actually be a good thing for you in terms of minimizing DVT risk.
It does sound to me like he's got it backwards, so go get some info from a reputable source and bring it to him at your next appointment. Just say "I remember we had discussed this last time and you said ABC, but all the information I received from other HRT providers says it's really XYZ. Could you clarify for me? I just want to be sure we're all on the same page." If you can have that available before you see your hematologist, that's even better. Get him on the same page and it will be harder for your endo to refute.
My provider also asked about my sexual history. I didn't take any offense to it, and she made a point to mention that that particular line of questioning wasn't any kind of judgment of me or my fitness for hormones, it was just to get a more well rounded view of me as a patient and to help me make the best possible decisions regarding my care. And it really did help at least in my case, because my doctor is a primary care provider for trans people. She's pretty well versed in what is and isn't available and what the pros/cons are to various procedures, and because she knows sexuality-wise what I'm into and not into, she's better able to give advice that's relevant to me. Since yours is just an endo, it makes less sense for him to need to know that, but I'm not really surprised that he asked, especially if he's older. My doctor remarked early on that I was "easy" and likely could've gotten HRT from most providers, because I'm binary and I prefer women. Some providers are still apparently stuck in the dark ages and can't fathom why you'd want to transition if you're gay :/
