I can understand the original idea that replacing one tyre, of a known tread and compound, with a new version of the same, should involve fitting the 'new' or more heavily treaded tyre to the rear (although, not an idea I agree with or comply with)...
But when fitting winter tyres, you are replacing both the tread pattern and compound (and in many cases differing diameters and tread widths) with something designed to work to a completely different set of parameters.
It makes NO sense at all, fitting tyres with a rubber compound and tread pattern optimised for use below 7 degrees C and/or snow, to the rear of a FWD car...and I don't care what anybody says...it's illogical and bloody stupid.
Front, or all 4....on a Golf.