The thing that makes the web different and why the idea of a living standard makes sense for the web is because (by and large) web changes can't break backwards

The thing that makes the web different and why the idea of a living standard makes sense for the web is because (by and large) web changes can't break backwards compatibility. Browser vendors are unwilling to make changes that will break existing websites because it could result in losing market share as users switch to browsers that still work for those websites. So anything currently in the standard today is expected to continue working tomorrow. That means even though the standard may change regularly, you can depend on anything that it currently says to keep working. The idea of versioned standards is only really important if you have to worry about things changing out from under you that could break your existing work.