We were all introduced to the
env() function in CSS when all that drama about "The Notch" and the iPhone X was going down. The way that Apple landed on helping us move content away from those "unsafe" areas was to provide us essentially hard-coded variables to use:
padding: env(safe-area-inset-top) env(safe-area-inset-right) env(safe-area-inset-bottom) env(safe-area-inset-left);
Uh ok! Weird! Now, nine months later, an "Unofficial Proposal Draft" for
env() has landed. This is how specs work, as I understand it. Sometimes browser vendors push forward with stuff they need, and then it's standardized. It's not always waiting around for standards bodies to invent things and then browser vendors implementing those things.