Perhaps it's the words. What's happening is not social transition. It's abuse. It's silencing women. It's erosion of women's rights. It's the abolishing of female only spaces. Calling it late social transition is like calling murder a facilitation of afterlife transition. But in the case of murder it actually means the same thing to everyone. As far as I can tell from others explanations, social transition is just pretend pronouns and forcing boys into girls spaces. So let's call it that.
I see what you're saying, and I appreciate that it sounds like a euphemism for what is actually happening (e.g. I wouldn't refer to someone having a double mastectomy for gender identify ideology-related cosmetic reasons as having "gender-affirming" surgery).
I find social transition to be a very helpful term personally, though, as it makes it quite clear that the thing providing the changes that person is demanding is other people. It's right there in the name, and there is no social transition without manipulating other people to comply with the demands.
To my mind, the words "social transition" do describe what's happening accurately, because (1) the only thing that's changing is how other people are treating the person (in that we all have to pretend for their benefit) and (2) the transition is required to be implemented by that person's social circle transitioning the way they behave, and without those other people providing that service to the person demanding it, there is no social transition.
Social transition is a service that other people provide to the person demanding it - parents might be willing to do that, and a school might (if it's been Stonewalled). But it shouldn't be the case that other people around that child, including the child's teachers and other children who have no duty to centre that child's needs to their own detriment, should be required to provide that service to that child.
Yes, the child might feel better if everyone bends to their will around them. That's the case for lots of things in life. But demanding it is not fair on others. And social transition without other people doesn't exist, hence the name. Which is why it is so problematic, because it only means anything if other people (including other children) are dragged into it, often to their own detriment.
One of the key arguments that trans people make around modifying pronouns is "it's not that hard", as if people's objection is because of the difficulty of the task. But what they don't seem to realise is that this comment reveals that regardless of whether it's hard or not, it is a task that takes at least some effort and it is an accommodation being asked of other people who don't necessarily want to support a movement they're fundamentally opposed to, or adapt their language or give up their own rights, just to make some random person feel better about their own life. The fact that "it's not that hard" is the best argument people can come up with for complying with social transition is the reason it should always be viewed (legally and otherwise, IMO) as a request as opposed to a demand. People need to be free to decline otherwise we are all just props in some random child's life.
I find it helpful to ask people pushing for it whether social transition exists without other people playing along, as it's the social element and the fact other people are having to transition their behaviour that gets to the crux of the issue.