The angle drive on the Aisin Warner (auto) and Volvo (manual) gearboxes are driven from the front differential crown as they are on the VW implementation - do not be confused by that O/S/F driveshaft passing through the transfer box because it does just that - passes through.
There is no mechanical layout difference between the haldex installation between Volvo and VAG, there are some software changes and I think Volvo has the better software.
If you look at this picture you can see the splined sleeve drive into the transfer box (bevel gear) as well as the splines on the driveshaft (it's from the latest Passat Alltrack).
If you're interested in this sort of stuff then you might find this interesting if you've not seen it before:
https://www.youtube.com/watch?v=dtx6w_WqVNs
There's loads of vids like this on Youtube... including a group test with about 20 cars.
The biggest factor in how good a AWD system is in snow and mud is
how good and well maintained your rear brakes are...