Easy, but probably not legal.
The guy even mentioned being able to remove the pin and change the position. The state AWB laws I've seen (which doesn't include California, and probably some others) say the stock must be "permanently" fixed. A removable roll pin is not permanent. In fact, he had a collapsible stock on a lower receiver. If he lives in an AWB state, he was illegal before he even turned on the video camera.
I know a couple of retired LEOs who run a small gun shop in an AWB state. They can't even bring a stock into the state and modify it -- they have to come in fixed. And what they told me is that the "fix" is epoxy. (Not a roll pin.) They buy ARs from Stag Arms and Bushmaster, mostly, and the stocks they receuve are solidly epoxied into position.