I think what Gom was saying is that once pitchers learn to pitch Pedroia on the outside of the plate, he becomes nothing more than a singles hitter.
That being said, he's full of s***. Every hitter is less effective if the pitcher hits his spot, either inside or outside. But Pedroia is one of the best bad ball and contact hitters in baseball and he's gotten more than his share of doubles by cuing an outside pitch down the line.