The article doesn’t make any sense. Anything will freeze whenever it’s temperature goes below it’s own freezing point. It doesn’t matter what the condition of its surrounding material is. It could be solid, liquid, or gas. The article seems to indicate that the mussels’ surface can shed ice particles easily, but it doesn’t explain at why it doesn’t itself freeze.
My understanding... It freezes, but it doesn’t adhere. It flakes off easily.