As I said before (which she did not respond to), the issue with this as some kind of requirement is it gives those carte blanche to harass people who they suspect as not being cis or not "passing" to their acceptance.
It's not a requirement, it's a guideline.
I don't think it's difficult to have some self-awareness here. If you're a transwoman who still pretty much looks like a man, then don't be surprised or offended if someone in the ladies room is intimidated and made very uncomfortable when you walk in. If you're a transman who still looks very feminine, don't be shocked when the guys at the urinal get edgy when you come breezing through on your way to a stall.
I don't think we need a law at all. I don't even think we need any additional social policing. It kind of pains me to say it, but if the handful of transpeople who cannot pass for their self-identified gender hadn't made such noise about it, I don't think it would be an issue at all. Because most people in society are polite in person. And most men aren't going to say anything if someone walks in who looks a bit more feminine than the average guy, because well, he might just be a really little guy. Most women aren't going to say something if a fairly masculine woman comes into the restroom, because well... some women are pretty butch, and it's impolite to make someone feel self conscious about their looks in that way.
It's been the handful of people who don't pass, who are still obviously their birth gender, and who are angry and upset that they can't use the bathroom of their choice who've drawn attention to it.
At the end of the day, I don't really care about public bathroom usage. It was a little uncomfortable for me going to the restroom with my niece when she first began transitioning, because she seriously could not pass. At the beginning, she couldn't even really pass as a guy in drag. It was just... awkward - for me, for her, and for the other people in the restroom. But nobody said anything, and it wasn't a big deal.
Where I do end up having some hesitation is when it comes to high school college, and gym locker rooms. We're simply not a unisex culture at the moment. Maybe we will be at some point, but we're not even all the way over our Puritan roots. And I just don't see how wedding tackle bouncing around a teenage locker room is going to be okay with most of the people there. Nor do I think it's a particular good idea to have boobies bobbing through the boys locker room with a bunch of testosterony high school boys. I don't think that's good for the natal or the trans boys.