If you are driving on the highway you are essentially in one wheel drive as only one rear wheel is being driven and the front is disengaged. If slip is detected, the front differential is engaged but only one wheel in front and one wheel in back. From there it only engages the other wheel on the axle by braking the slipping wheel. So technically, the best it gets at any given instant is two wheel drive, one front and one back. When active, the abs is monitoring wheel spin and applies the brake on the slipping wheel to start driving the wheel on the other side. In a true AWD system, all wheels are driven at all times and the viscous couplings distribute torque 100% of the time automatically.
At least that is my understanding of the operation. IMO it is not and never has been AWD.
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