My perspective on this issue:

MoI 4, 5beta1, and 5beta2 were filling up the screen completely.
But, by hitting the Windows 11 upper double box at the top left, (The Maximize/Restore icon) to the right of the minimize dash, then draging the reduced MoI window left, then right,
all 3 such MoI versions then leave the Windows 11 task bar at the bottom of the screen.

- Brian

Hovering over the Window 11 Maximize/Restore icon in Windows 11, pops up 6 possible window pane varieties. (Customizable???)
For Windows 11, the Window Maximize/Restore icon in MoI 5 beta does not have this hovering behavior.
(I am speaking from much ignorance :-)

Is this some new feature of Windows 11?
YES, it is called snap layouts.
https://docs.microsoft.com/en-us/windows/apps/desktop/modernize/apply-snap-layout-menu


(I am already getting annoyed by the Windows 11 "weather report +" button at lower left popping up on my screen " :-( )