
Whatever - M+S refers to the tread pattern. Winter tyres are often M+S designated too - they also have a little snow flake symbol on them to show they are designed for low temperatures. The two things are not mutually exclusive.
Anything tested in extreme cold & designated ****hot will have been winter tyres, not just any old M+S pattern tyre. In fact in most countries that regularly experiences extreme cold winters, the law states that they must swap to winter tyres - not M+S tread pattern, but winter rubber compound.
I agree that most tyres have different compunds, just as most have different tread patterns - no one tyre is best for everything, they are all compromises
Read the link that Zip posted earlier in this thread.......
Anyway I defer to your clearly awesome knowledge

there's nothing more I can add to this debate and will sign off at this point.