My 02 has 3 modes, selectable on the fly (though the rear and front wheels have to be centered for it to switch):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.
a) 2 wheel steer
b) 4 wheel steer which is speed dependent
c) 4 wheel trailering mode
The truck crabs during lane changes at highway speed in trailer mode, which is interesting when you intentionally try to "crack the whip", in ice skating parlance. The truck's tail does not fishtail out, the trailer merely follows the hitch ball. Was messing with abrupt lane changes, pulling a 3,000 lb dump trailer, and it was like the trailer wasn't even there. Hopefully. they bring Qsteer back with the eSilverado and its GMC twin.
Low speed crab would be possible on the Quadrasteer with a control module reflash...how to get the source code, lol?