What broke
The workflow document instructed every mission to apply a label no mission could apply, for weeks; the governance check was green on every day the four labels did not exist and green once they did. Thirteen others had been created by hand as missions needed them, twelve with the default colour and eleven with no description.
The rule it paid for
Creating a label and applying one are two different acts; the check verifies that the document names a label, never that GitHub has one, and says so.