There is a bug in the interaction animations between the "parent" (player who initiates the taunt) and the "child" (player who presses G to interact). When the "child" receives the taunt, they clip through the parent's body due to incorrect animation. Specifically, the Heavy plays a jumping animation instead of staying grounded as intended.

The taunt itself is really cool, but Valve messed up the implementation, lol. Hopefully, they’ll patch this bug before it becomes too noticeable for everyone!