I remember my daughters being read in a simular way when she was about the same age.  It was my understanding that they were trying to supress growth at that time.  If they could surpress the bone growth at an early age, then they had a better change of "extending" the growth period, and get the maximum height out of our CAH kids. 

My daughter is now 10, so it has been a while, but I think that is what I understood at the time.  She now has advanced bone age 1.5-2yrs.  She is quite tall and thin.  Her dr is happy with her height and bone age, she expects my daughter to be average to above agerage height as an adult.