That sounds totally over the top to me for forehead surgery. I did two FFS surgeries, upper face and then lower face a year later with a little over 7 hours surgery each time. In neither case did mine ask me to stop HRT beforehand but constriction "socks" were placed on my legs during and after the surgery and I was also given anti-coagulant before the surgery. It increase the levels of post surgery bruising but does significantly decrease the risk of DVT.
Interestingly, because of the bruising issue, I requested not to use the anti-coagulant for my second operation and two weeks after the surgery I experienced a small thrombosis in my wrist where the I.V. had been placed. It was mostly a scrare as the vein really swelled up but I still ended up in the emergency service of the local hospital.
However, at the end of the day, it is the surgeon who makes the rules...
Best of luck.
Donna