Reminds me of PWM [1] on old PC speakers. Many old computers (e.g. of the 286 era) had a speaker that was only able to generate square tones. By controlling the start and duration of the pulses, programmers could generate sounds that were a lot more rich than what you would expect from "plain" square waves [2].
In a way this is similar: they start with two actuators that seem very limited in what they can accomplish: you can only speed them up and down. By modulating the speed of both motors in sync, they are able to control that cheap rotor mechanism they came up with, achieving 6DoF [3]