Bro, it's not that simple. Height is also down to environment, weight and nutrition. Humans are also, on average, getting taller. I've read a bit about the ancient Neolithic cultures of the Nile valley and Levant, and they are all reported to be short or average height (which makes sense given the natural environment and nutrition back then).Nilotes carry West-Central African admixture and are not ancestral to Cushites. A pre-existing population they descant from do, but not modern-day Nilotes.
Also, I am fairly light for a Somali.. not a hint of Niloteness in me.
The height is a trait of the original Cushites. Most male Somalis I know who were raised in Western Europe are above 6'2''.