I think the main point of this feature is that it breaks the video out from a window in the existing page.

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?