Without taking anything away from the author, calling MOV a "single instruction" stretches things quite a bit. It's more of a big family of instructions that happen to share an assembly mnemonic.
But if you look at the serious attempts to implement OISC, you'll find that the "single instruction" has so many parameters, some might think it might as well be a big family of instructions.
Yea this isn't a true OISC setup, but it's very close and still completely impressive that this technique even works. That you can influence all necessary registers like this and accomplish arithmetic isn't immediately obvious.