I have a couple of issues using a Surface Pro 8 (my desktop at home does not have this problem despite all being the same versions etc).
1. The Taskbar does not extend to the top of the screen but a gap of about 1cm. But all the MS app maximised come up to the bottom of the Taskbar which is good
2. You can't really see it in the image below but there is a transparent grey box which above and around the Start button- doesn't effect the operation at all
Latest version of Win 11 and also Start 11.