The labialized velar consonants are rare even in historical Japanese; besides (possibly) one verb (kweru), they (kwa-, gwa-, kwe-, gwe-) occur only in some Sino-Japanese morphemes. In Japanese, they merged with the non-labialized versions (ka-, ga-, ke-, ge-) as late as the early 20th Century.
But do they remain in Ryūkyūan?
Or, did they even exist in Ryūkyūan? Obviously, Ryūkyūan also borrowed multiple Sino-Xenic terms, some of which must have been necessarily present: such as name of the goddess Kwannon. Do we know the current status of words like this? Even if such words are Sino-Japanese borrowed from Japanese, did the labiovelars remain in Ryūkyūan even when, very recently, Japanese stopped pronouncing them with the //-w-// glide? Unfortunately, the vast corpus of scholarly work, to my knowledge, rarely deals with the Sinitic layer in Ryūkyūan.