The AWD is permanent because is a differential permanetly engaged. It will lock the center ONLY when the difference in speeds between front/rear AXLES is high for a certain time - like when your front or rear wheels are on snow). Otherwise is a 35/65 split (normal driving).
If it was like you assume - VC only on front axle - then how do you explain that the rear would work with the front axle removed?
For example - if you suspend a wheel on a non-locking/limited split differential, than the other wheel will not turn. The suspended wheel will turn with double speed. In your case, the front "empty" flange will spin with double the speed and the rear will not budge.
And if you say 4404 it is not a differential, then explain why are those satellites (part #320) present in the 4404 and what that annulus is doing there (part #322)? More about that:
http://en.wikipedia.org/wiki/Differential_gear#Epicyclic_differential
If you see, the rear shaft come from the 225 that is connected inside the annulus 322. The front shaft is connected via the 83, 18, chain 90 and gear 63 to the INSIDE part of the VC (#64). The outside of VC is connected inside the annulus 322, therfore directly to the rear shaft.
So liquid inside VC - the shafts spin independently via the differential and chain. If liquid solidifies inside VC, the front and rear shaft are solid connected (the chain ratio is 1:1 and the epicyclic ratio give the final ratio beween the shafts torque/power).
Input shaft goes inside the sun part (#65).
Last from me: Even if I am wrong, I would not run my AWD without the front shaft. Becaus eonce you remove the shaft and the VC is fried, you cannot put another one back in, will bind. If the VC doesn't fry running hot for months in row, then it is a great pice of engineering.