there are lots of other functionalities that SSMS assumes you must have sysadmin rights in order to perform actions;

most of the nodes in the Object explorer assume it, scripting of objects is one example i know of off the top of my head.

example: create a user with VIEW ANY DEFINITION and login as that user into SSMS. you'll get errors whenever you expand any nodes, when in theory they should be able to view it (that login can see the metadata via queries, of course.

CREATE LOGIN ViewAnyThing WITH PASSWORD = 'NotTheRealPassword';

GRANT VIEW ANY DEFINITION TO ViewAnyThing;