This is normal. The icy or dusty sector flags determine which resources can be mined if asteroids are present. Dusty sectors also negatively affect the productivity of solar power plants, while icy sectors don't have other gameplay features. The icy or dusty flags also affects the color correction or possible debris field.

Ah, is there no tag for the presence of asteroids?

I had just assumed that Dusty corelated to having Asteroids, but maybe that is just common but not always true.