There are small visual differences between stock start menu in Windows 11 and Start 11 on Windows 11 (and Win 10 for that matter too). Like shut down menu:

Win 11:

Start 11: 

(Start 11 shut down menu looks awful tbh, possibly a placeholder?)

A shade/transparency of the lower part of menu:

Visual difference between lower part and part with documents and icons (lower part is darker).

There is no difference in Start 11.

Also, size of icons on that lower part is different. Pretty sure medium shortcut icons in Start 11 are a tad smaller than in stock Win 11 menu.

Different search box:

Win 11:

Start 11:

etc.

I wonder if these differences are to be removed at some point, or they are kept on purpose, because of some copyright reasons or so?