> why isn't this interface implemented in any browser yet Partially because in addition to the interface itself it relies on a bunch of generic worklet machine

> why isn't this interface implemented in any browser yet Partially because in addition to the interface itself it relies on a bunch of generic worklet machinery which also doesn't exist in any browser and is not trivial to implement in non-sucky ways. But also partially because the spec has kept mutating, so no one wants to spend time implementing until there's some indication that maybe that will stop.