Now, what’s the <https://caniuse.com/> link to this feature?
It's a bit early for browser support given that it's not usable in Chrome. A better place to look for information about the status is probably here:
I think it might be this one?
https://caniuse.com/selectlist
The blog post says that "we're excited to see this feature progress through working groups and standards bodies" but doesn't link to anything that would help figure out which standard this ostensibly implements.
In the first paragraph of the article there's a link to the relevant WHATWG issue[0] (they could have used better link text though; of all people Google employees should be cognizant of link accessibility).
This is specifically not selectlist. "Previously, the Chrome team was working on the idea of a selectlist element. What's described in this post is that feature redesigned to reuse the existing select element instead."