When you install the startup file on the current version of Word for Mac (16.18 and 16.20), you get an error every time you start Word. It reads:

Compile error in hidden module: 'mdlUpload'. This error commonly occurs when code is incompatible with the version, platform, or architecture of this application.

It does add the MoodleQuiz ribbon item, but you get the same error when you try to use anything in it.

Digging a bit deeper in VBA, it seems that the library "Microsoft XML, v6.0" (MSXML60 I think) isn't available, but is used.