If a spa receptionist informed me that a trans woman was using the female section I might understand that to mean:
- a woman who considered herself the opposite sex was using the spa because she is trans identified - and as a female she would be expected to use the section that aligns to her sex and that might be her preference.
- a man who has had genital surgery to have his penis removed following extensive therapy (male transsexual)
If you weren't up to date with the most recent lingo, you might think this was a transvestite.
(Clearly the person in the spa that was complained about and has claimed responsibility, is neither of the above.)
If the spa receptionists were informing female guests as they arrived, they should do so before they paid and they should use explicitly clear language so they can make an informed decision. I would put money on the mother who took her 9 year old daughter into that section of the spa was not informed or for argument's sake, let's say she was, she didn't expect a fully genitally-intact male to be naked, and certainly not in front of her daughter with a semi-erect penis.
Some might have had the Be Kind approach but expected the male to use a private changing room and not to be dick-swinging. I would have expected any males who have even the smallest amount of respect for women and children, to use the men's, and to do this so to avoid accusations of sexual assault or child sexual abuse apart from anything else.