We create invisible buttons for socket tooltips because sockets themselves aren't buttons and because we don't have a special tooltip handler for the node editor. Currently those buttons have an empty right click menu with just the "Edit Source" operator. Changing to label buttons removes the right click menu but keeps tooltips working. This didn't work earlier because label buttons didn't have tooltips. That has been implemented in the meantime. Pull Request: https://projects.blender.org/blender/blender/pulls/131399