That a person’s past should be left in the past is a fine principle and when someone does something as radical as transitioning gender the stakes are raised.
But this is a dangerous point for trans people. When there are still states where the trans panic defence is allowed in a court, disclosure can be a matter of life and death.
Personally, as a lesbian, who is mid-transition (it’s a LONG process, especially with NHS waiting times for gender-affirming surgery. Though I acknowledge it’s a massive privilege to be able to access such treatment for free) I always disclose that I’m trans. Plenty of cisgender lesbians are still attracted to me. But some balk at the idea of a penis, regardless of how unpenislike it is now (hormones mean it functions exactly like a clit). I respect other people’s genital preferences. Largely because if someone is so shallow as to find my outward appearance a turn-on but won’t touch my genitals to please me then I probably don’t want to be with that person. I’ve dated a pre-everything trans woman myself and had we become intimate it wouldn’t have bothered me at all. I was attracted to her as a woman. I’d have engaged with whatever plumbing she had because of any love I had for her.
Sadly, every aspect of trans people’s lives are endlessly examined and litigated. And the general public seems to think they have a right to know of our trans identity. Indeed we’re constantly labelled as deceitful. And the ‘shock’ of sudden discovery is enough to let some killers walk free.
So non-disclosure can make us targets. And disclosure puts us in the crosshairs of transphobic hate mongers. We really can’t win.