They work on the premise that the fish's mouth will be closed when you set the hook, so the cam action of the hook will turn the point up/down and make contact with the inside of the mouth ... rather than the lips or membrane ... giving you a better hookup, with less likelihood of tearing a hole in the membrane & possibly losing the fish (if you give any slack or the fish flops or turns).
To my way of thinking ... they're "technically" sound in that idea, but a regular Aberdeen hook has about the same percentage of possibility of doing the same thing. I wouldn't call them a "gimmick", but I wouldn't give them any greater credence than a normal hook.
But, I'm also saying that from limited use of them, and no recent use of either style.