It actually has nothing to do with 4WD or AWD, the article is poorly written and confuses several terms. At the surface 4WD is manually selected and AWD is 4WD all the time. Thats it they are the same thing, it's just 4WD means you opt to put the vehicle in 4WD.

The term the are talking about when traction is applied to the wheel with the most binding to the ground and away from the one that has the least traction is called a Limited Slip Differential and by virtue of the slipping of the low traction wheel it will spool the high traction wheel and bind it transferring torque to it. This can also be done by what is called a locker, either electronic or manual but manual lockers can be dangerous at high speed if you are not used to their manor. You generally only see manual lockers and welded differentials in offroad trucks. Limited Slip differentials and electronic lockers are available in both 4WD and AWD vehicles.

The term they are talking about to apply power to both the front and rear wheels is not a differential but rather a transfer case and it is not always at a 50:50 ration man times they run 60:40 or 70:30. Both 4WD and AWD have a transfer case, 4WD's allow you to select whether they are engaged or not.

The term they are talking about when they talk about adjusting power front to back is called a Traction Control Unit and is handled by a Body Control Module that may or may not also communicate with the Engine Control Unit or the Transmission Control Unit to defuel or detorque the powertrain, as well as adjust torque via electronic lockers in the differential to the wheels that need it and away from the ones that do not. As well as engage or disengage front and back axles via the transfer case. Many newer AWD systems have this but it is also available in most newer 4WD vehicles.

TLDR is 4WD and AWD can be virtually identical depending on the subsystems but the article confuses a lot of those subsystems as being unique to one or the other. Though the upper end of 4wd's have more "hardcore" options not generally found or offered in AWD vehicles.

I found the article very good explaining the basics and history of awd vs 4wd. What you explain is the status of today's 4wd vs awd, where indeed the features in awd vs 4wd cars can overlap a lot and because of the big variety of implementations quite hard to understand by regular Joe

A typical 4WD without locking diffs will still spin wheels. You have to have differentials at each end to go around corners on pavement.

An AWD car has _3_ diffs, one in the middle that splits power F/R, and then one at each axle that splits it L/R.

Highend 4wd setups can lock the diffs so all wheels spin at the same speed all the time - essentially on slippery ground, but very counterproductive when you actually have traction.