so my summary now on how all subaru might work
front-back: some if not most can go 10/90 - 90/10 torque transfer: if that's true wow
left right: they use a fluid to stiffen the wheel with no traction transferring torque to the wheel with traction. not sure how effective but perhaps pretty ok.
if BOTH are true you could get 80% torque going to ONE wheel??? (number made up: assume left rear is the only wheel not spinning the centre diff will transfer 90% torque to the back and of that 90% the rear axle diff sends 50-90% to the left rear)
of course just a guess ... who knows in real life without precision testing haha
to add to the legacygt.com post - the new forester has an X mode + CVT ... so that post needs some updating :D