They showed the MOC in other photos, and we see how the head is attached and how the torso is built. There’s no room for a MS motor in there. Plus, you can do a lot of sneaky stuff with CG. Captain Disillusion goes into great detail about how you can do stuff like this.
That said, since this is clearly a hoax, it’s possible that OP just outright lied and made a different MOC from the one shown in the original clip that looks similar enough to pass off as the real deal.