Anyone Know Why The Michelin XPS Is Not Intended for Winter?

Thanks for the replies. I suppose I'll call Michelin tomorrow and get to the bottom of it. I'm hoping it's only a recommendation for people using them as steer or drive tires.

I use the trailer in the winter for skiing and snowmobiling so it's used in the snow and ice. I bought it last year in December with these tires on it so I haven't used them it's entire life but they've worked fine for me so far. I didn't know they weren't rated for the winter until I went looking for new ones.