4 year old swaying back and forth

A 4 year old that I take care of during the day has this problem with swaying back and forth. Like he can’t talk or play or watch tv without swaying back and forth.

The parents are concerned but I’m pretty sure it’s just a form a self soothing, right??

His pre school teacher will grab him by his hips and hold him in place so that he can talk without swaying but I feel that is a bit much?

What’s your opinion