Its not outdated. There may be multiple variations on AWD (as i mentioned, some can vary power to individual wheels, rather than just the axles), but 4WD (or 4x4) is categorically not AWD.
Doesn't traction control further blur that? Given that traction control is now required almost everywhere, and involves cutting power to individual wheels (Not like ESP using brakes), at what point does traction control cutting power to individual wheels or axles dynamically in a 4x4/4WD system make it an "AWD" instead?
Perhaps those vehicles that use 4x4 in the tradtional sense are such that you have to engage it and that effectively cuts also any traction control - and then you disengage for normal driving?
Traction control on an AWD system can be composed of power management (overall torque output), power distribution (how much power goes to each axle/wheel) and braking (slowing down individual wheels).
Traction control on a 4WD can only consist of power management and braking, because there is no way to vary the distribution (otherwise it would be AWD, not 4WD).
There are some systems that under certain conditions will switch from 2WD to 4WD. Those systems are NOT considered AWD and dont have the benefits thereof.
FYI, ESP (Electronic Stability Program) is just a brand term for an ESC (Electronic Stability Control) which covers both TCS and ABS. When people talk about "traction control" they usually mean the entire ESC subsystem.
I think part of why I consider them to be one and the same is because in the total absence of "true" 4WD/4x4 (approximately no one drives pickup trucks in Europe, I'm guessing that's where the true 4x4 still lives in the US) so the 4WD/2WD moniker has been used for 2WD/AWD as in "Will you get the 2WD or 4WD tesla is used somewhat sloppily?". It seems car manufacturers though are still careful not to call anything 4WD or 4x4 when it's not.
Not all AWD implementations can adjust power per axle. The vast majority just use a center diff that is either open or limited slip. Both of those configurations are also used in some 4WD systems.
The primary distinction is that AWD is full time, while 4WD is part time and vehicles run in 2WD until the transfer case connects the second diff/axle.
Actual torque vectoring AWD systems are fairly rare and expensive compared to the AWD that has existed for 50 years, though they are becoming more common.
To clarify, your initial statement said "a locked center diff" would be a valid form of AWD, which is what i was contesting.
All the differentials mentioned in your link allow for variable power distribution to each axle. Thats the whole purpose of a center differential.
Of course, not all AWD are created equal. Some apply equal torque to all wheels (i.e. open), some prefer a single axle (e.g. limited slip), some aren't controlled by the wheels but by the ESC (e.g. electronically actuated clutch packs). I suppose in electric cars where each axle is driven independently they dont even need a center differential (but I have no knowledge there).
But its an interesting link nonetheless - it was certainly educational - so thanks!
I do agree, however, that a full-time 4WD (which have a central diff, unlike part-time 4WD which generally do not) are effectively indistinguishable from an AWD with a simple open center diff. Of course, those are the least effective types of AWD - but the 4WD at least has the ability to lock that diff and likely has a multi-speed transfer case :)
Perhaps those vehicles that use 4x4 in the tradtional sense are such that you have to engage it and that effectively cuts also any traction control - and then you disengage for normal driving?