(At the end of this post I attached a .zip archive)
No - I only need Start11. I recently noticed this behaviour with two different clean Windows 11 installations with nothing more installed than Start11.
I always installed Windows 11, then fully updated Windows 11, then installed Start11.
Then I adjust different Windows 11 Personalization settings und Start11 Configuration settings.
I run into this behaviour every day(for a high chance the line at the top of the taskbar additionally shows a bright color which partly replaces what's otherwise completely dark - dark is the desired appearance) - this visual glitch is happening very often to me on every work session when I return from an fullscreen application to the Desktop or when I simply boot or reboot my machine normally.
The taskbar stays in this new vertically splitted dual colored appearance permanently and only a manual refresh(Taskmanager - right click Windows Explorer entry - choose Refresh) would always restore the desired look of a fully black colored line.
The update process with a manual Windows Explorer refresh takes about 2 seconds. During the update process the taskbar visually changes the whole line from the strange looking mixed color appearance into a bright appearance and from there it switches back to the dark appearance.
These screenshots are exactly representing all my personal adjustments in Windows Settings and Start11 Configuration - with these you can eventually replicate the issue:
download the screenshots to begin investigations with my preferred settings .zip