Having driven my RWD biased 4WD Explorer for 6 years in all kinds of weather and having driven my father's previous RWD 98 LS400 in the snow several times, and driving my FWD ES300 in the snow for one season on top of having taken advanced driving courses in skid cars and on tracks in BOTH RWD and FWD cars I agree there is a difference, but that difference is more subtle than you suggest. For the average driver, that difference is VERY subtle. My ES300 is excellent in the snow, much better than the RWD LS and getting close to as good as the Explorer, believe it or not. You just have to remember that the FWD car is going to understeer more, so that means slower into the turns, and you can't use the engine to help steer around corners. Sure the RWD LS and the Explorer had less understeer and you could use the throttle to help round curves, but that doesn't do you much good if you're sitting back at a stoplight spinning the rear wheels on the LS. RWD may be more predictable in snow, but you've got to get it MOVING first. I side with most of the driving public that believes, for the average situation and the average driver FWD is better in the snow than RWD. Now put snow tires on a RWD and you've got a different story.
I can believe the RX's system seldom shifts torque to the rear. If they're as good as my ES is in the snow thats seldom neccisary. The only time I'd really want my Explorer over the ES in the snow is when it starts to get past 6 or so inches. Several AWD systems are front biased, the much touted system by Subaru, the system by Audi, the system used by Honda and Toyota vehicles such as the Highlander and of course the RX. Sure its not going to be as surefooted as a GX or an LX with a real transfer case and a low range but it will get you to work and back in 7 inches of snow just fine. Anything more than that and the vehicle is being used outside of its purpose. Check out an Infiniti board like freshalloy.com and see how many of them complain about how poor the FX is in the snow (rear-biased AWD like you said) then check out the Lexus boards and read how many have issues with the RX in the snow. Apparently front vs rear bias aren't the be all and end all to the equation. My parents didn't have any issues with their FX in the snow last year, but it was all over that board, accidents, people just plain afraid to drive them (I think it was mostly 45s with the 20in wheels, my parents have a 35 with the 18s).