Traction control in Prado

I know the basis of it is to stop certain wheels spinning when losing traction, applying the ABS to which ever wheel is spinning. I did a Watagans trip last week and we had heaps of rain so obviously certain parts of the trip were extremly slippery. I noticed when all 4 wheels were in the mud and I accelerated all 4 wheels were spinning together, BUT if I put say one side on the grass (not as slippery) the ones in the mud would set off the traction control.So Im presuming that because all wheels were spinning at the same time (centre diff locked) that the traction control unit would be thinking that all four wheels are turning at the exact same time due to the mud that it wouldnt activate the traction control ?? I have tried under certain driving conditions like say a sharp left taking off from a stand still and give it a gutfull the left front will activate the traction control and the lights on the dash indicate which wheel lost traction. Does this sound correct. I would have thought in mud it would do the same but too my thinking if the centre diff is locked 50/50 power front and rear and all 4 wheels spinning together then there is no difference in traction on any corner ??? Regards Steve