When is that?

With the poles at the 1 minute mark, the robots enter holding them and their left hand never moves on the pole. Also note the stationary hand is matte grey while the moving hand is metallic silver.

Likewise with the wine gourds (?) at 2m30s and the nunchucks at 3m40s.

It’s a completely sensible design decision, much simpler to do cartwheels and vaults if you don’t have super delicate fingers fitted.

Probably a compliant magnetic coupling, as even simple force-sensing mechanical hands cost too much to practice back-flips. =3