It's called a swash plate or a gimble . Each servo is mounted and connected to an opposite axis. One x and one y. Neither servo will ever fight the other because of how they are mounted. It's a great idea though it just takes more hardware. The benefit is that the swashplate holds most the weight of the head so servos have minimal work. Good find !

I'm working on a universal joint that pivots high (just below the ear) and using push rods on the x and y. Servos connect similar as in that hack.

I'd like to add that the joint arrangement on there is better than the U-joint I'm using. There is less flexibility in mine because at the 45, 135, 225 and 315 degree points I can only bend 30 degrees. At 0, 90, 180 and 270 there is full 90 degree bend. To me this is plenty as I foresee I will only use 30 degree tilt anyway.