It's true because it's statistically true. The rational according to an article (in Baseball America, Collegiate Baseball or one of these last year) is cold weather position players don't get nearly the reps warm weather players get creating less position prospects. Therefore many more pitchers are drafted from cold weather than position players. The article was about the potential change in this philosophy with the number of indoor training facilities popping up in cold weather regions. But we're way off topic now.