Clearly you've never actually looked at IT when he was standing next to anybody.
The NBA does official measurements at the combine. Believe it or not -- these are public and very much real. Certainly more real than someone's "hey he looks small on TV, must be 5'6" assessment of height.
And why would you be surprised that a 17 year old in the middle of a growth spurt might have a different measurement a year later?
I'm surprised when a 17-year old in the middle of a growth spurt
shrinks by an inch and a quarter in height over the course of two months, while his arms mysteriously grow three quarters of an inch longer. Aren't you?