ABLS just applies the brakes to the wheel that is slipping and redirecting it to the other wheel with more traction. Of course you can over power this with lots of skinny pedal. It will not transfer any power to the front or vis versa. No certain two wheels will spin every time. It depends on the situation. The ABLS does a good job and it's a lot better then just being open diff. I was able to get my back driver's side wheel off of the ground about 4" by climbing a small rock and the ABLS got me there.
A first gen couldn't even get the tire off of the ground because of being an open diff. Once the wheel was fully unloaded it started to spin like mad. So going in order: open diff followed by ABLS and finally the locker. Those are the best ways for traction. Open diff being the lowest and the locker being the highest. Also one other thing to keep in mind with ABLS is that it has a sensor that detects brake temps so if the brakes start to heat up then the ABLS system takes itself off line to prevent you from having no brakes when you really need them the most.
A first gen couldn't even get the tire off of the ground because of being an open diff. Once the wheel was fully unloaded it started to spin like mad. So going in order: open diff followed by ABLS and finally the locker. Those are the best ways for traction. Open diff being the lowest and the locker being the highest. Also one other thing to keep in mind with ABLS is that it has a sensor that detects brake temps so if the brakes start to heat up then the ABLS system takes itself off line to prevent you from having no brakes when you really need them the most.