Again with the statues? /sigh...

Some statues do not prove or infer anything. They are statues that prove nothing, absolutely nothing, other than the Mhachi were evidently able to sculpt them.

The modern city-states all have racial diversity of varying degrees. There's no reason to believe the Mhachi didn't have the same, so some Highlander Hyur and Roegadyn would totally make sense even in a Lalafell-dominated society (as the implicit ancestors of modern Ul'dah, it makes even more sense). Those are likely the inspiration, and even if they weren't a minority population in Mhach itself they would know of the other races. As for the corpses, I'm going to guess they're either Hyur or Elezen.

They're statues. They do not necessarly mean anything.