That does not sound correct--when I hear "front and rear locker" I think of something that locks the diffs. Pretty sure Toyota is relying on "electronic" traction aids here for what is otherwise an open diff: the brake on the spinning wheel is used to grab the spinning wheel, thus enabling torque to the non-spinning wheel. Still an open diff though, still sending equal amounts of torque to each wheel.
The button tells the (whatever controls the coupling that is what we'd think of in the transfer case, save the fact that there is no real transfer case, just a transaxle that somehow does both transmission and transfer case duty) to do 50/50 duty. Otherwise the car just takes off as FWD, kicking in RWD as slip is detected. Which is an awful thing to do in snow, to blow away front tire traction before bringing in the rears. By hitting the button you're telling it to engage the rear proactively, to not wait until it (too late) detects wheel slippage. [Maybe it kicks in the rear, the harder you hit the gas, and back when they had the V6, I suspect they again had different programming. Still. It's FWD biased.]
I'm guessing "snow mode" in other makes is doing something similar, biasing torque to the axles in an attempt to avoid wheelslip. It's just that many the CUV's are something of a slip & grip sort of AWD, which works for many people, in many situations, but... is still a slip&grip when anyone on this board really wanted a proper locked center diff in the first place.
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