Most organizations are flexible, they don't have to be flexible to what you think is flexible. WADA says right their on there page they give medical exemptions.
This thread is about HRT, no I don't think HRT is natural, and if anyone does then they are just playing mind tricks on themselves. If I lose an arm, then get a bionic arm, is my pitching in the major leagues "natural" because hey I have two arms like every one else?? No it isn't. Natural and synthetic doesn't always also mean one is better either.
Do you think athletes should be able to compete against natural athletes in say the olympics on HRT as long as their levels are not above the higher end of ref range for testosterone?