I am shaking my head that this is even an issue. The world really is going downhill.
In a sensible world, people would be free to set sensible boundaries for whatever bathrooms are within their control, and decide for themselves how strictly to enforce those boundaries. If you have a shop, and you want to designate a single bathroom as "employees only", but you're willing to make an exception for the parent whose kid is doing the potty dance, that's cool. If you have a couple of single-stall bathrooms, and you put a "man-ish-shaped" sign on one and a "woman-ish-shaped" sign on the other, but you don't really care as long as people are being mature, that's cool too. Even if the signs aren't "enforced", I as a customer am generally going to follow them just because I think that's the sensible and courteous thing to do. And if a shop owner is going to be a jerk about it, well, I don't like to buy from jerks anyway. For schools and for libraries, let the administrators set rules that are simple and sensible and agreeable to local parents. There is no reason for a one-size-fits-all rule here.
But that's the thing that started this whole mess, at a city level. Charlotte decided to impose a one-size-fits-all rule. Even worse, their rule was, "no rules are allowed". Telling people that they are *not allowed* to set their own common-sense rules on their own bathrooms is stupid, overreaching, and a bad idea.
The State legislators saw that it was a bad rule, but they made the same mistake, just in another direction. They started by making a law, "Cities can't make a law like Charlotte's". But then they ended by making their own new one-size-fits-all rule. C'mon guys.