sounds to me like you’d have to have some stuff posted online under your real name for it to find and match to
They probably only need a reliable IRL ID for one of them. That's a weaker requirement than posting under your name. Your name can be discovered other ways. For example browser fingerprinting, where that fingerprint is also associated with a "KYC" login elsewhere. There is a whole industry for using non-name signals to ID people. Big data is powerful.
Ofc there are ways to frustrate that. Yet the attacker only has to win once. The defender has to win every time.
But it will be statistical in nature. They'll have some confidence attached to it. That could be very low, or quite high. Depends on how much you have disclosed online.

I think that's what it is.
What it is today. But these things tend to slip-slope their way to worse privacy violations over time. Oh, children are getting around the setting? Well, we better tie it to a government ID.
I'm more afraid of what it becomes than what it starts as.