This change was introduced in Office 365 a few months back and is nothing to do with Windows 11 specifically.
The change was made to allow users to show the quick access toolbar (QAT) independently of the ribbon but in some ways the settings are now more complicated / confusing ...
The Access & Save icons are part of the title bar as
@The_Doc_Man stated and cannot be altered or removed UNLESS you hide the title bar itself
Here are 6 possible settings you can use
1. Title bar (with 2 icons circled in red), expanded ribbon & QAT (highlighted below ribbon
2. Title bar, minimised ribbon & QAT below ribbon menu
3. QAT above ribbon - notice that also includes the 2 title bar icons (so I have 2 Save buttons as shown)
4. QAT hidden - title bar and minimised ribbon only
5. QAT hidden - title bar and maximised ribbon only
6. Application window removed - borderless form 'floating on the desktop
Hope that helps clarify things