I think the original point was that pitchers generally throw "about 5mph slower than they are clocked in game" from ops article

Fleisig isn't alone; few others have seen 105-mph heat either. The Guinness Book of World Records still acknowledges Nolan Ryan's 100.9-mph pitch in 1974 as the fastest ever recorded. Yet pitchers Joel Zumaya and Mark Wohlers have since thrown 104- and 103-mph fastballs, respectively, since Ryan's throw, but Guinness didn't certify the results from the guns used to measure them. And that may be for good reason. In his lab, Fleisig says that pitchers generally throw about 5 mph slower than they've been clocked in games. He says that is due to a myriad of variables with the radar gun clocking the pitch, including the manufacturer and where it's positioned in relation to the pitcher.