People in the ancient world generally frowned on any sort of physical disability even if it was injury from war. Exposure was a common practice not only for Spartans in the movie 300, but most ancient and many primitive societies. It's very likely that steppe nomads would have engaged in similar practices if children appeared physically disabled or deformed, as they did not have the resources to support extra people that, at least in their view, could not contribute like a "normal" man or woman.

That said, children that were exposed could also be adopted by another couple looking for a child. This happened in both Greece and Rome. Perhaps it's also possible that a sturdy looking child, even if it had an unusual facial appearance, would be expected to grow up into a physically strong person and somebody might keep him? For a female however, I think that would be almost impossible as they would struggle to attract a mate in later life.

Overall, I'd say they were generally exposed.