I've not researched on trucks as much as I have cars, so actually the 10 degrees was quite a surprise for me.The rear tires don't steer that much - the four wheel steering (4WS) section starts at 4:38, and he says in the crab mode part that the rears can only steer 10 degrees or so, which is typical of 4WS systems. Crab mode could be handy, but few of many 4WS road vehicles made so far bother to include it. GM themselves did 4WS on a previous truck - the Quadrasteer option for full-size pickups of 2002 to 2005 - and even though the 4WS system was entirely electronically controlled (no mechanical connection to the front steering), they didn't provide any manual tweaking or mode selection and just set rear steer angle based on front steer angle and road speed. Quadrasteer was capable of up to 15 degrees steering angle - a lot more than the Hummer EV allows.
Most of the cars with 4WS today have the rear steer about 3-5 degrees, while newer ones are starting to get more angle (e.g. 2021 Mercedes Benz S-Class).
Well, now I know even 15 degrees was done 15 years ago. I learn something new everyday!