Comment by zehaeva
This feels like you'd say that just because apples fall from trees and a bowling ball falls in much the same way when tossed off a building, that grouping those things together implies a common cause and that we should call that cause a theory because we aren't 100% certain that they are caused by the same effect.
They could be two different reasons.
I do prefer Occom's razor for these things. We've seen a bunch extremely large celestial objects move in ways that our models cannot account for with the things that we can see. Sure, there could be more than one thing out there causing all of those extremely similar effects. But that's far less likely than there just being one reason.
It's pretty reasonable to invoke occam's razor for claiming that in general unexpected galaxy rotation curves have a common explanation. It's another thing to claim without blinking an eye that these are phenomenologically connected to baryon acuoustic oscillations in the CMB (which is what Angela does)