Well, a lot of these things are really opinions, or colored by your feelings about them. If I call my dog a sweet little old girl, does it sound wronger if it's an 80 pound puppy GSD with an "old soul"?

But suppose you're right and we disallow anything outside of the opinion category, unless it can be shown to be objectively true. What if my keister was purple, because of the color of my pants? No opinion there. Ugly purple no-good keister sounds about as right or slightly better than ugly no-good purple keister.

I agree that the rule seems plausible because lots of parts of it work, and lots of examples of things sounding right or wrong come to mind, but it seeming plausible doesn't mean it's true, if that makes sense. I would want to see statistics. I want to see someone say "we ran this corpus of 30,000 books through a computer, used this natural language processor to categorize every string of consecutive adjectives, and found that such and such percent of them fit the rule perfectly. The violations were mostly of so and so"

Tbh I'm probably not going to do it or look into it too much, I ain't got time, and I'm sure there's a grad student this would be perfect for. But without a more rigorous analysis, I'd hesitate to pass on the rule as if it were true.