Head stays in place during squatting

I am working on this method of rigging (10:08) https://www.youtube.com/watch?v=e85HGSAS80g

In short, the method has me create a frontal folder that contains both the head and body. "Frontal" is tagged as a head, as is "Head". A draggable tag is added to "Frontal" at the base of the head. This is supposed to be a good method for manipulating a puppet to squat and jump. The video explains it better than me.

Anyway, followed the instructions in the video (at least 3 different times). Everytime I've tried, it works perfectly from the shoulders down. But the head moves significantly less that the rest of the body (it

does move a little bit) and the neck stretches really long. I've checked every layer for fixed tags and everything seems to be in order. Any ideas why this is happening?

Before and after dragging puppet into a squat: