The video mainly demonstrates how to add a tail to a Metahuman and enable the tail to move automatically through physics simulation.
The synchronization of the tail and body movements is primarily achieved by using “copy pose from mesh.”
https://dev.epicgames.com/community/learning/tutorials/ppV1/unreal-engine-ue5-6-tutorial-how-to-add-a-tail-to-metahuman-and-tail-physics-animation