Thing is though RK, while I don't know whether HRT would cause a shrinking of a penis although I accept that it is a possibility and the functionality of a penis may be affected, BUT what about those trans who do nothing except say the magic words?
As you say, there's a group who don't take hormone suppressors nor hormone supplementation whether for medical reasons or because they believe insisting on this is a violation of human rights. See, e.g.,:
Jillian Bearden and Rachel McKinnon have much in common as cyclists, Olympic hopefuls and transgender women — and much in conflict as opposite poles of an intractable argument over how to balance what’s fair with what’s right.
Bearden agrees with the International Olympic Committee that naturally occurring testosterone gives transgender women an unfair advantage in competition against cisgender women, meaning women who were born female, while McKinnon believes subjecting trans women to testosterone blocking violates their human rights. ...
How to reconcile science (blocking testosterone) with human rights (competing as you are). ...
eu.usatoday.com/story/sports/olympics/2018/01/11/these-transgender-cyclists-have-olympian-disagreement-how-define-fairness/995434001/