Yes, it's true that you have a better view of the plate from behind the pitcher than behind the catcher. This is why, in games where the PU has almost no responsibilities other than balls/strikes, and plays at the plate, that he moves from behind the catcher to behind the pitcher. Surely we've all seen this done in MLB playoffs, when they work with 6 umpires, or in the NCAA College Softball playoffs, when they have 3 or 4.

Actually, the best view of the plate is from a bucket near either dugout.

Seriously - if your pitcher has ANY curve at all, you have NO chance of calling an accurate zone from behind the plate. You might survive a game when everything is perfectly straight, and every pitch is thrown from the center of the pitcher's plate. Maybe.