Kevan you are missing one of the main points in both the links, which is, in most of the other European countries it is mandatory to change your wheels in winter. It also talks about reduced accidents due to the use of winter tyres during winter.
I agree with your point about friction that friction is a factor of mass. But to achieve higher friction you should have proper area of contact between the tyre and road surface. This is exactly what winter tyres achieve. They are made of harder compound rubber, have deeper grooves in the tyres for keeping the water/snow/mud out and prevent aqua planing. Also most of the winter tyres have lesser width compared to their all weather/dry weather counterparts.
Also one last thing is dont just consider the air temperature to be the temperature of the road. Esp during evenings and night times the temperature of the road is much lower than the air temp.
Esp we are worse off having RWD cars during winter time, so we more than any body have to look into this and swap the tyres for safety reasons. Or at least this is my opinion.
Cheers