I don't agree with you at all either, with a good studded tire I've never ever had a problem with any sheer ice. I've ridden on a lake with the slickest ice I've ever seen, roads, etc. Studs worked great with my Schwalbe Marathon winters with 4 rows of studs. I cannot say with certainty that I've run into every possible form of ice, but I do live in Minnesota, it's pretty icy here.

It's snow + ice that it's impossible to deal with sometimes. Snow by itself is hard to get through, but if you fall over you've typically been slowed down to almost a stop before it happens. Ice is handled great with studs. But snow on top of ice ****s under you, the snow shifts around under your tires while your studs aren't long enough to actually hit and catch on the snow. I would much, much rather ride on pure ice with studded tires than ride on a snow + ice combination.