Quite right. There's nothing wrong with a dash of UML as seasoning or a visual of some actually critical process, but just like you wouldn't want to eat a half pound of oregano on top of your steak, you don't want to produce as much UML as code.
It is hard to capture certain details in prose, and a (nearly zero effort) emitted UML diagram can do the trick. Or at least convincingly make it look like you did the trick...
But start from UML? I think I'd rather spend that time polishing my cv.