HA ha. I would read "4 piston brake" and expect something exotic, like an upper an lower pair of calipers like on some cars. Instead, they mean a caliper has two pistons on each side, and you have a front/rear. Hence 4 pistons.
Nonetheless, good searching, Timpo. These kits have built in cut off wiring. I bought a pair of Zoom hydraulic brakes w/o the brakes (which I added myself). They do work smoothly, and it's easy to buy/replace new pads. I wonder if the unit you linked come with the hoses assembled and filled.