I wonder why they need tree motors per axle.
For the AMG GT4 there will be 3 motors: two at the rear, and one at the front.
My interpretation (and my German's pretty lousy) is that each motor is combined with a gear system in a single package, and they're calling the overall package (motor plus gears) a High Performance Electric Drive Unit (HP.EDU).
The two rear motors will probably be independent, so no need for a mechanical rear diff (it'll be electronically controlled).
There's no mention of a front diff, so it's unknown whether that's built into the front HP.EDU or is a separate mechanical diff).
With separate front and rear electric motors, there's no center differential to worry about, and a sufficiently sophisticated motor control system can make it behave well on and off road.
What would it mean to "turn off" traction control in a car with independent motors per wheel? (OK this is a 3-motor/4-wheel scenario, but hypothetically…)
With software control and independent motors, we're likely to see increases in low-traction capability (for the right price-point and probably aimed at particular buyers)
Then there's braking. More driven wheels means more braking energy that can be recouped via regen. In traditionally rwd cars you lose out here because braking energy tends to be directed forward.
Also there's packaging. One large motor might impinge on the cabin.
Also you get benefits wrt mass production.
A smaller motor is easier to handle. Potentially could avoid the need for high voltage cables. Which eases repair.