I really don't understand this kind of nonsense that has grown around the trans movement, being "left out" of everything... how? Nobody in the UK is or ever has been denied treatment or dismissed for being trans - where endo is concerned I imagine any dismissal of concerns is going to be because you are a woman first and foremost, as even without endo, women are often told anything menstrual or pregnancy related is "not an illness".
And how is being trans anymore relevant to endo (or the million other things they're "left out of") than anything else that may impact a woman on top of endometriosis? You don't see any other group - women with anorexia, schizophrenia, cancer, paraplegia etc doing this and just those four I've picked off the top of my head are all as prevalent % wise in the population, if not more than being trans, I'd wager they worsen endo more than being trans would too.