Yeah I saw that too, it does it in one other place, the feet are also sort of gliding around. If you look at the people in the background a lot of them are doing the same, and there are other temporal-mechanical inconsistencies like joints inverting half way through a movement, i guess due to it operating in 2D so when things are foreshortened from the camera angle they have the opportunity to suddenly jump into the wrong position, like twitchy inverse kinematics.

Everything also has a sort of mushy feel about it, like nothing is anchored down, everything is swimming. Impressive all the same, but maybe these methods need to be paired with some old fashioned 3d rendering to serve as physically based guideline.