When we deselect the filters and switch to the Player layout, the filters are re-selected again and the rectangle control becomes visible in the Player.
The workaround is to select a track header or a clip with no filters, but it would be nice if the filters would remain deselected when switching layouts.
A simple thing we could do when you choose that layout is to Select None in the Timeline. However, that is not perfect and may not be coded in because the timeline selection ought to be kept for when revealing the timeline. The main problem is that there is an elaborate sequence of events I have not figured out that makes the first filter be re-selected.
In any case, the Ctrl+D shortcut to Select None is available even while in the Player layout as a workaround.