I actually think this rule is a good one to apply whenever you’re creatively stuck. Would it make sense if I made the idea bigger or smaller? Sometimes even a simple distinction like that can create something twice as interesting as your original idea.
Would your song sound better with an orchestra playing it or just a single violin? Should you amp up the tension in your story or pull it back.
As the old school novelty guys say, “Bigger is funny, smaller is cute.” Which is not true for everything, but is definitely true for underpants.