What? That's why this winter the roundabouts of Britain were littered with BMW's?
Yes. I didn't say that RWD was better for the snow, only that the tires do have more grip under acceleration. It's just that the grip is converted into a snow blower, not forward motion.
It's simple physics, when setting off in snow you creep too slowly for the weight to really shift back, but in an RWD there is less weight pushing the driven wheels into the road than an FWD meaning they have less traction and will spin up.
Unless friction is zero, you'll always be pushed on a solid surface. The problem is, snow isn't always solid. If the friction force between the wheel and the snow is greater than the friction force between the snow and snow, the wheels will just tear up the snow.
If your car is stuck before you even move, then no drivetrain will save you. Like I said, unless friction is exactly 0, the car will move.
You're trying to treat snow like a low friction version of tarmac, but that doesn't work. Snow easily deforms, tarmac doesn't. It's the deformation that makes snow driving what it is, much like with rain. Rain isn't just dry grip * .5. With rain varying water layer depth, currents and flows, and deformation by tires contributes to more complex dynamics than what is seen on dry road.
That's why the snow comparison doesn't really translate to dry road.
A bit of an anecdote, but a 4WD Audi got stock on my block over the winter. Some one with a truck tried to pull it out, he got stuck because he was just digging snow. Who came to the rescue? A puny ATV on huge tires. The ATV was light enough compared to its tire area that it wouldn't sink. It pulled the truck out and then the Audi.
Narrower tyres also help as the weight is concentrated to a smaller surface area again increasing the traction applied from the engine.
Narrow ones would increase the pressure on the ground, causing the car to sink potentially. Winter tires take advantage of this through treading, but the goal isn't to bump up friction, it's to give the tire more surface area. Though this isn't an issue in GT.