It doesn't replace Greydwarves, they are still the most common in Meadows at night. In fact the Fulings only rarely spawn in groups of 3—and none of them will ever be starred.

So, rare spawns and Greydwarf/Skeletons are far more common. I don't mind it at all and when I do run across them I just consider it a nice delivery of 3 Black Metal to my main base.