Right. I've got a Golf R with Haldex; it allows 30+mpg under cruising conditions but can "lock 100%" in the sense that the fronts and rears are locked together. It's created a lot of forum wars because some people read the marketing materials saying "100% of torque to the rear wheels" or "max 50/50 split" and don't understand the difference. If it's fully locked, on dry pavement, of course you're getting 50/50. If the front wheels are on a magic 0 friction surface, of course, all of your torque is going to the rears because the fronts have nothing to grip on, but they're all spinning at the same speed (theoretically).