I think it’s more like saying an F1 car has very rigid and precise turning *because* of its wide, blocky tires. Thinner tires with a rounder profile, like a normal car, are more floppy and flowy, throwing the weight of the car around a bit more. Obviously suspension plays a part there, but there’s a reason race tires are shaped like that.
All he’s getting at is the square edge and extra width of the fuller-shaped wheels gives you a little more leverage and stability vs. a classic shaped wheel, which effectively makes your trucks narrower due to the outer edge of the riding surfaces being slightly closer to center. Classic-type shapes feel more tippy to me as well. Easier to roll them over onto the shoulder, giving you a little more lean/swerve/movement than a comparable Conical or OG-type shape.