This is a bit hard to explain so hand in there. This is with Start11 set to show in the centered taskbar.
Using Start 11 Modern Style or the Win11 style (maybe any choice) in Win 11 ver. 22000.282 x64...main button click once on the centered Start11 icon (I'm left handed) brings up the Start11 menu screen (good)...before it closed another main button click on the Start11 centered icon should close it...but it doesn't - instead it brings up the Win+X menu. Note: also an alternate mouse button click on the icon will bring up the Win+X menu as it should. BUT, the problem is the 2nd click should close the menu not bring up the WIn+X men.
This behavior does NOT happen it the Start 11 icon is on the left...only when centered. !
NOTE: configuration is set to have the start11 icon launch the Start 11 menu. If you choose for it to launch the default Win11 menu that works as expected: 1st click brings up Win11 menu, 2nd click closes it.
On the 2nd monitor with this set of configurations the 1st click brings up the Start11 menu and the 2nd click closes it - as it should.
BUT: on the 2nd monitor an alternate mouse button click brings up the Win11 menu and not the Win+X menu.
IF the configuration option is set for the statr11 button to launch the WIN11 menu and the windows key is set to lauch the Start 11 menu...the 1st and 2nd main mouse button work as they are expected to on both monitors: 1st click=win11 menu, 2nd click closes it, alternate mouse button open win+x menu. And, hitting win key once open Start11 menu, hitting it again closes it.