Open differentials (without traction control) send power to the axle (or drive shaft) with the least amount of grip or resistance. Whether that be three open differentials (like the Grenadier or Defender) or a 2wd Jeep with only the rear differential powered. Only by locking ANY differential (front, center or rear) do you split the delivery of the power across the differential. By locking the center differential you split torque 50/50 between the front and rear, and by locking the rear you will split torque between the rear left and right. The same applies for the front.
This is why, based purely on mechanical, open differentials the Grenadier was immobilized by lifting a single wheel.
The Grenadier does employ "brake traction control" or ETC, as illustrated in this video:
View: https://youtu.be/lLFzv7FJy3g?si=oDZ94pqqzP1PudvU&t=332
My assumption is that in the previously referenced video, they have turned ETC off (if this is possible) for purposes of illustration. Brake traction control, coupled with a locked or unlocked center differential can be quite capable. - as illustrated here:
View: https://youtu.be/LUdQ4WgRbgE?si=T9sxYdoBiFYn82q-&t=60
Regarding "all-wheel drive", it really depends on what system you are using. Modern "all-wheel drive" systems simulate locking differentials by monitoring the wheel speed sensors and applying the brakes and/or by using limited slip and or electronic locking differentials in the front, center and rear.