I’m not sure what you’re trying to say here; pulchritude twice as rare as disharmonious, which is relatively rare. It’s an order of magnitude rarer than effervescent, as an example, which is a word I would consider uncommon but in most people’s vocabularies. And given how much more common pulchritude is - surely physical beauty is one of the most common subjects in any language - while disharmony and effervescence are more complex and rarer in practice, I think it speaks to how little the word is used. Its synonym, beauty, is used 2000x as often.