On my iPhone if I full screen a video I get the native iOS video controls. (I.e. volume, full screen, etc). On my ipad (2018 model) I get the web controls still in full screen. This makes scrubbing the videos difficult as i have a couple of pixels of red progress bar at the top I must pixel perfect touch to move through the videos.
Exiting and entering full screen also appears to break if used too much. I presume the browser just isn’t being identified correctly (As you give proper iOS controls on iPhone) and something needs to be tweaked.