But that's the same in any all wheel drive car. No one buys an all wheel drive car if they've an interest in maintaining drifts. If thats what you want it's like asking a cow to lay eggs, and you need to buy a different car. All wheel drive of any type is not a drifting platform, and will only do under fairly severe provocation, and it requires more power to do it. Rear drive is a must have if you want drifting.
The focus RS does strange things with its diff-less GKN rear axle to provoke a simulated drift, but it's as fake as the 17 year olds "drifting" in the McDonald's car park by putting serving trays under the rear wheels and leaving the handbrake on. The AMG E-Class was a rear drive monster to start with, it was tamed with all wheel drive to keep the majority of the public interested and sell a few more of these mental widowmakers to people who recognise the limits of their own talent, but AMG have acknowledged their customer base seems to choose them over their dynamically superior competition because they like their over-engined minicabs to have a bit of rear drive more-power-than-grip lunacy, so they have joined the have-cake-and-eat-it club by retaining the gimmick, USP, and techno-geekery to provide those thrills if desired.
All these things, the mustang line lock, the Focus drift mode, the AMG make-it-more-dangerous mode, are the brainchildren of the same bored over caffeineated engineers who gave us switchable exhaust noises and launch control, and are looking to add a bit of silliness to the cars and their own workdays. The manufacturers, keen to exploit just about anything that can be seen as fun, different or a potential sales advantage, sieze upon these things and copy each other. Audi though? This is a very serious company, one that has eschewed basic things like steering feel, proper weight distribution, and fun, because a car with those things no longer feels like an Audi.
Audi won't offer drift mode on their cars for some good reasons, like the fact that haldex doesn't lend itself to such trickery. The rear axle could be over-driven by changing the rear gearing, but then the clutch slip would require some very heavy clutches, and a huge loss in efficiency. To do it 'properly' they would have to ditch BorgWarner and contract GKN to provide it in the smaller cars, which would be an enourmous and costly re-engineering exercise. In the larger cars they've just spent a fortune engineering Quattro ultra, a system so anti-drift that it physically disconnects the rear propshaft at both ends and is 100% front wheel drive, up to 100%of the time.
Most of all though, they won't do it because they lack the sense of fun required to do such a thing.