They work way more than that. They practice, study opponents, and travel. Travel for work is working. They go to community events and make appearances. That is work.
Not like I feel sorry for them, but keep in mind that it is not just jumping that demolishes their bodies, although the jumping I am sure does a lot of damage.
These guys are really tall and heavy with muscle, so even running on the hard wood surfaces for years is going to mess up your joints.
I went to the same gym as Chamberlain here is los angeles for a little while That guy had really messed up hips, all sticking out. His joints are totally ed. He played way before the high flying atheletes of the 90's, and he didn't need to jump as much because he was taller than most players.
My point is, many of these players have serious health problems after a 10 year career. If you asked me if I was willing to trade making a few million for being in a wheel chair, or even using a cane after age 40, I would say no thanks.
Putting so much strain on a huge body by playing pro sports, when these giants are already is going to have a tough time as they get older, evidently is leading to many retired NBA players to have a substantially shortened lifespan:
https://billypenn.com/2015/10/01/mos...dary-nba-bigs/