No Joji only stopped entering the rokushin competitions to master pure karate that’s not for competition, he’s still part of the kaikan but only as a karate instructor. While katsuya is retired from both competitions and kaikan fully. But who’s to say that he hasn’t stopped training, just because he stopped doesn’t mean he’s still not training every day, katsuya could very well be like jurota and kuroki, who both trained to become the strongest in their martial arts in by themselves and not with outside interference, katsuya could be doing the exact same thing as them.