This sounds like an awful outcome for female players. Truly. I don't want to judge what you do or don't know about basketball specifically, but it's a huge part of my week, particularly coaching junior girls at a pretty high level.
The current procedures in place for Basketball Victoria make much more sense.
(I linked to them in an earlier post, but for ease of reference : https://www.basketballvictoria.com.au/cdn/fy7f4fune5ck4sss
Effectively, at sub-elite levels (which includes high grade representative basketball, including what I coach) people can nominate their gender. A trans athlete can list as and play as a girl.
That is MUCH preferable from my point of view than throwing boys and girls in a single pool once puberty hits.
One of my daughters is a good player. She plays as a big, standing about 5'6" or so (12 years old).
If she plays against boys, of course she might be better than them, depending on their skill level. But playing against boys COMPLETELY changes the game for her. It is a totally different sport. I'm happy to specifically go through why, but unless you're invested in basketball, I'm not sure it would make sense for either of us to go down that rabbit hole.
Suffice to say, she doesn't want to play against a bunch of relatively more athletic, fast, tall people who are pretty crap at the game. She wants to play people who are good at the same, and play with skill, and push her to be the best version of her self.
I've been used as a practice squad player against state level women before, when I was much younger. The people I had to guard her miles ahead of me in terms of skill. I was a crash test dummy basically, who could smother them with my length, speed, and strength. (I'm a 6'0" point guard, or at least I was back then) They were much better basketball players than me by any measure, but they hated me guarding them in practice (which was kinda the point), as it would completely break aspects of their offence.
BTW, the 'grow up and face the fact' thing is a little simplistic for my liking. I spend a lot of time coaching in women's sport, go to more professional women's sport than mens, and have an enormous amount of respect for female athletes. My position is about ensuring there is active, high-level competition for women. That has NOT been an easy journey over the years, and it's taken a lot of effort by a lot of people to slowly build it. I am a tiny part of that, but I would push back hard on any thought that I think male basketball players are 'better'.