The new "visual update" of Office is now becoming official. This cosmetic adjustment makes the productivity suite match the new Windows 11 look, although some users still on 10 might also see the update. It mostly functions to add the new rounded corners and dark themes to 4 of Microsoft's classic work-focused apps.
https://www.notebookcheck.net/Microsoft-s-Windows-11-compatible-visual-refresh-of-Office-is-live.582906.0.html