Beyond the questions of winter weather properties, there are adjacent tradeoffs between the tire types (outside of studded):
1. Fuel economy
2. Noise
3. Degree of particulate pollution emission
I'm sure that the all-season tires probably have some negative tradeoffs in these regards to, which yields a choose the most optimal product for the time of year. All-season tires to me seem like a convenience food for places where the weather can be legitimately bad.
One other difference that is hard to articulate to North American drivers with respect to understanding Scandinavia and roads: there are places where snow and ice will literally not be removed (maybe not even removeable) from the road when plowed (I presume until spring melt). It just becomes a thick ice pack over the course of weeks. I never encountered any roads in my life (including Northern Minnesota) that were this inclement. North American roads tend to be cleared (plowing or melting) to asphalt or pavement.
If tires complying with the standards overlap, then the standards are meaningless. When there's requirements for snow tires, but not for X brand or model of snow tire, than it's not doing any good. That's why it's important to have a snow rating that can apply to tires of any type, and if it meets that rating, regardless of the rating for dry warm weather, than it should be good to go, otherwise not.