Why do you think that was fake?

Low quality motion. The robot's movements have no inertia. Too smooth, too artificial. Like how video game characters move without motion capture.

There's also too much ambient occlusion in the rendering, but they were careful with the materials and the scene that it looks somewhat plausible.

Compare it with an actual video of their real robot: https://youtu.be/48qL8Jt39Vs?si=Kkb7oTnYf-GllRJv

The difference in the movements is clearly visible.