Precisely. And science will always be vulnerable to 'but you can't explain X'. Because we've never been able to explain everything. Turns out the world is COMPLICATED. (I mean, who knew, right?)
But that's no reason to shut down debate. Sometimes, when you can't explain X, it's because you're just plain wrong. And you'll never figure that out if you don't listen to people arguing with you.
Just to be clear, it's quite possible that the Xoh are more advanced than our people in some ways. For instance, we have the Jungian perspective on behavior neatly enshrined in our gods. "Alien, but knowable", "Teacher, but devourer" is a hybrid of anima and shadow. We don't really know the Xoh religion at this point, but it could reasonably enshrine a more Piajetian or Freudian perspective on psychology which could be quite handy for our Shamans.
The Lowland Minors are not the Xoh, they are the Xoh's former whipping boys. I doubt they are advanced in anything really since most of their time is spent in subsistence farming and low intensity war.