Now that's some quality evidence. Textual proof that:
Goats are a thing on Roshar.
They're called "horses" by Rosharans, but they...
Are distinct from the horse-horses people ride.
Horse-horses are shod.
So that's pretty conclusive that normal horse breeds on Roshar are not goats, but what we would recognise as genuine horses. It doesn't on its own mean that Rhyshadium aren't Giant War Goats, because if anything it reads that they're well suited to rocky terrain, aren't shod, and goats are called horses.
Together with the WoB about them being genetically close to normal Rosharan horses, though, I think that narrows down my hope to one small possibility: that Brandon was talking about the goat-horses, not the far more widespread horse-horses, in that WoB.
I think that's stretching the limits of believability. I concede the point.