E.g. they were also first to support the `:has()` selector/pseudo-class, which I think can be useful for avoiding JS in some cases.

That's not what it is. It's a typographic control that wasn't available in browsers before. It's got nothing to do with fonts being badly made. All textboxes (no matter which font) can be measured from many different places, and this lets you specify (via text-box-edge) which of those many different places you want to consider as the bounds of a specific textbox.