My point about the front tires pointing in the same direction is that that because they both turn to point into the curve, the outside wheel turns closer to the same speed as the inner wheel than the rears do since the rears are fixed perpendicular to the axle. Since the point of rotation in the curve is not the center of the vehicle or the front of the vehicle, but closer to the rear of the vehicle, the rear wheels do in fact experience greater differentiation than the front.

Since A and B travel more nearly the same distance than C and D due to the vehicle pivoting at the rear, a locked front axle has less impact on "jump" and "bind" than it would in the rear. This, some believe with good reason, that if you are on the cheap, and want the best of both worlds on street and off road, means a locker in the front and Truetrac in the rear accomplishes better handling on and off road.
Of course selectable lockers on each end would be the best, but I don't have that kind of money to throw at axles. Of course locking one front wheel is not like posi trac, but it is safe on road in snow or patches of snow as it easily allows the steering axle to have different wheel speeds and provides extra pull. Since the rear is not locked from the get go, it will also behave better on road, but provide needed traction off road - especially when the fronts are locked.
If you end up stuck on road in snow, obviously you just engage the other hub.