I have a 4-in one hub, they work pretty well,just have to allow a little more time for all of the ESCs to ack. If you have a KK2.1.5 the throttle passthrough does the exact same, by passing the raw throttle in to each motor at once.
Basically, the board sends a pulse which is sampled by the receiver and sent to the ESCs. If the timing of the ESCs isn't calibrated, it will result in the motors not spinning at the same rate. This is one of the causes of quads flipping on takeoff and erratic flight
