That is not true, a couple of years ago the NBA mandated that before every season every player be officially measured without shoes and weighed, with the results both posted on the team website and sent to the league office. That was when we learned Kevin Durant was 6’10” and not 7’. The other day I posted the heights without shoes of some of the guys who played locally. Jarrett Allen is 6’10 1/2, Nic Clayton is 6’11”, and Mitchell Robinson is 7’. The number of centers below 6’ 10” is small.The heights you see listed for guys in the NBA are with shoes on. Cliff was measured 6’9” without shoes on. Any NBA center you see listed at 6’10 or 6’11 is probably actually 6’9”