I don’t think this theory applies to CAH kids as they are often over treated in the first year or two of life and therefore growth can be delayed.  My own son was quite small in infancy, measuring 75.5cms at 18 months and 81cms at 2 years. He is now 18 years old and 173cms (and still growing!).  Growth was always my major worry as he was the smallest kid in the class for years but although not a giant now at 5ft 8" (and expected to gain at least another inch),  he is well within his genetic potential.  He didn’t take growth hormones.