I mean it's limited to content managed by the browser, whereas the native WM way works for all apps.
I'm curious how the WM could detect that the a portion of a window is playing video, and break that out into it's own movable window?
I'm not sure how you do that without the browser managing that.
I can then interact with that video separately from the page. I can scroll around on the page, I can open other links. It decouples the video from the page.
There's lots of ways to open new chromeless window, or set a window always-on-top. That totally makes sense to be in a wm, but that's not all this is doing, right?