DNA gives us insight into ancestry that has no parallel in astronomy. When we finally sequence a creature, we pretty much know right on the tree where it goes and stupid fucking crabs and everything that look like them can all get placed in their proper relations when previously purely dissection and observation misled those taxonomy pioneers.

you can't have that kind of bait and switch on celestial objects because what we see is what we see.

The reason that Pluto was smaller than predicted was the fact that the mass calculations assumed a single central object when the perturbations were made by the PLANET/moon system. That doesn't change the fact that it has enough mass to deform into a spheroid and orbits within 20% of the orbital plane.