> I’m curious how well this will actually work in practice

You're experiencing it working in practice. RFC9849 is a published document, the end of a very long process in which the people who make this "actually work in practice" decided how to do this years ago and have deployed it.

This isn't like treaty negotiation where the formal document often creates a new reality, the RFC publication is more like the way the typical modern marriage ceremony is just formalising an existing reality. Like yeah, yesterday Bill and Sarah were legally not married, and today Bill and Sarah are married, but "Bill and Sarah" were a thing five Christmases ago, one of the bridesmaids is their daughter, we're just doing some paperwork and having a party.