It's fairly common for women to start taking estrogen post menopause because their estrogen levels drop, and that can cause issues like losing bone density. I believe HRT was originally developed specifically for that reason, and it was only later that they tried using it to treat gender dysphoria.

But in this case, they specifically call out being a femboy on HRT, which I think pretty clearly says that they're on estrogen for that female figure. Whether it's DIY or just informed consent is anyone's guess, though.