How do we know what to use, without having some sort of snapshot that browsers can aim at and developers can evaluate?
The same way you do with snapshots. Browser vendors don’t look at the last snapshot, they look at the ever-progressing latest text anyway. No browser ever implemented all of HTML4, for example, even in the years after it was a formal Recommendation. Nor did they wait til they had done all of HTML3.2 before working on implementing HTML4. They all picked and chose the bits they thought were useful. With the Living Standard approach, we can also update the specification at the same time to remove the bits they all agree are useless, and to add new features that they think we should add (before they go off and invent their own solutions!).
