Nice find - but this works for audio only, and only if you don’t open any other apps. I’m talking about being able to minimise the video to a small window while you use another app. Unless I’ve misinterpreted your instructions.
but, yes, i must have misunderstood your requirements. the steps let me have the video running while the device is locked (for music, voice, etc). this was always possible in some way or another, but since the last patch it works out of the box.