It's a basic DOM element — a block of content. Without native support, it's simply shown by default, instead of hidden by default, so nothing is broken, and even the default on non-supporting browsers can be changed with JS and CSS.
If anything, this is the works everywheriest of things that "work everywhere" in post-2010 web development. Some other stuff actually breaks accessibility by default.
Given that Edge has less than 5% marketshare globally (depending on the source of the information), I would say that fretting over compatibility with it is not a priority. And given that MS is moving Edge to Chromium rendering engine, I assume this will solve the compat problem.
5% can still be a decent number of users, and tends to trend even higher in certain segments (state and local government, smaller "old economy" businesses)
If anything, this is the works everywheriest of things that "work everywhere" in post-2010 web development. Some other stuff actually breaks accessibility by default.