ok, but Santana was called up basically as a warm body when the Twins found themselves carrying 14 pitchers all the sudden. Gardy was still happily writing in Florimon at short even after Santana arrived.
I'd submit this is not just a recent phenomena, nor is it less prevalent for pitchers. It's a function of talent, not philosophy. Thorpe is the youngest player in the Midwest League by what, four years? Exceptional talent has always risen through the system fast; Hrbek, Blyleven, Carew, Wynegar, et al from the past. Arcia, Santana, Gordon, Thorpe, Polanco, Vargas, Stewart, Pinto, Rosario, Buxton, Sano....it's a very very long list of prospects who are among the very youngest players at their level.
Give Santana credit- he continues to hit and has made the most of his opportunity in center. He has really improved there. You can also give the Twins credit by trading Fuld so that Santana can continue to play center full time and learn.