I’m not sure what that video said, exactly, but both water and dirt move because they are both affected by tidal forces.

Tide is caused when an object, like Earth, is large enough to experience a difference in the effects of orbital gravity from one end to the other. The center of gravity of an object does not experience tidal forces.

Since most of the Earth’s surface is water, and the water is on top of the dirt, the water should be affected more by tidal forces than the dirt underneath it.

The video may have been talking about how the dirt affected by tidal forces also pushes the water, causing a compounding effect or something.