Isn't Roy Hibbert from Queens and son of Trinidadian and Jamaican parents? I doubt it has as much to do with migration in terms of basketball as much as it does with size.
My old lady is from the south, Louisiana swamps south. People down there are just bigger than dudes up north. Where I grew up in Brooklyn, 5'7'' is a normal height for a baller whereas down south its usually 6 feet and taller.
I do agree with the weight lifting comment in the article. In my High School, it was either basketball gym for PE or Weight Lifting gym. Most dudes took basketball gym because everyone wanted to shine whereas only dudes interested in football and soccer teams took weight lifting.