You are not saying unreasonable things, but none of what you said precludes a trans kid’s parents accepting them for what they are. You would do the same if you had a trans child, wouldn’t you? In the OP’s described scenario, I’m having a hard time blaming the “boy”’s parents without knowing much more. It’s difficult to know how best to steer your child’s thoughts if at all. If I thought my child was just wanting to change their gender and organs out of the blue with little other evidence of their being trans until teenage, I’d push back or at least try to identify if external factors like media and peer pressure might be causing it. Most of the difficult cases are intersex cases where decisions are not easy, and sometimes can cause irreparable damage physically and mentally, but parents can only go by what their kid says they feel, their best intentions for their kid’s well being, and what the doctors tell them. So blaming parents of trans kids doesn’t get us anywhere good.
As for parents of other kids in school, put yourself in the position of a trans kid’s parents and ask what kind of a school environment you’d want. I’d want the environment the OP describes. But, if I were the OP, I’d of course also understand that it might feel unfair to my daughter, but would nevertheless teach my daughter to err on the side of compassion towards her classmate, assuming that the other kid and his parents are not gaming the system, so like the OP, I’d want to know more and would probably take up the principal’s offer to discuss it in a PTA meeting.
In most school communities, kids and parents already know because communities are usually small, so the OP’s described scenario of not having any information about the “boy”’s condition or the parents sounds rather strange.
Lobbying etc. is different from parenting and local community, and is a political activity.