Jerry is 100% correct...can't say I've ever seen a weak armed catcher per se. To throw hard any player has to have the intent. As with most players, young catchers don't do enough long toss/arm strength development.
The transfer is important so that you don't waste your arm strength and is a quick place to examine when a catchers POP is lower than it should be based on his throwing velocity. You have to be proficient at all phases of throwing, transfer and recieving to maximize your potential at throwing out runners and becoming the best catcher you can be.
A catcher has to be able to throw using a couple different methods depending on the pitch location. The main problem with the jump/pivot is the catcher losing body control/direction and his weight distribution when he lands. Way too often I see catchers (at every level) being too tall and with too much weight on the front foot, leaving nothing to throw with. Too often coaches are watching for the end result versus how it happened.