It is a simple phrase that does not need to have a label, so I do not see usefulness. Therefore, the cursor is not as if we hover on a simple phrase without label.
I'm not sure why they opted to use label instead of something like span but it does in fact have a use. The overlay closer class it's assigned closes the overlay when you click it.
This is all setup for error overlays and things like the inline error messages. Clicking an error message that relates to a form element actually focuses the element.