Players cooking the books is a known fact. The paradox is it goes both ways. Shorter players add height to appear taller. Very tall players ofter shave a few off to be listed as shorter. It seems everyone wants to be a forward.
The most famous example is Kevin Durant, an obvious seven-footer (you can see him standing next to Boogie in the cover photo), but he is listed at 6'9. KD explained he didn't want to be labeled a power forward and 6'9 is the "prototypical small forward" so that's what his listed height is. He also added, "when I’m talking to women, I’m 7 feet."
Kevin Garnett did the same thing, and Flip Saunders would refer to him as 6'13 - KG felt that as a seven-footer he would immediately be slotted in at center, and he felt his best position is the power forward slot.
The NBA is putting an end to all of that, and in 2019 we will finally have a standardized measurement for all players. The tipping point was when we realized Buddy Hield's age was listed incorrectly. Hield surprised everyone when he revealed on the NBC Sports California broadcast that he turned 26 on Dec. 17 and not 25, as previously listed. In his case, it wasn't nefarious; it was a matter of wrong data entry - which he didn't go out of his way to address. So, the NBA is expecting teams to send in real data in the following week.
This should prevent situations like the one with Jason Thompson when he was listed at 6'11'' and turned out to be quite shorter. He seemed genuinely surprised.