That's like saying a mass grave of Athenian soldiers must be from Marathon. The Himerans (?) doubtless fought dozens or hundreds of battles which might have led to these burials. So the archaeologist automatically assumes the burials are from the only that is famous.
In 409 B.C., Carthage waged a new war against Himera, conquered, and razed the town. "All the people were slaughtered or deported and the colony never rose again," Vassallo said.
I guess "deported" is sort of accurate. Losers at the time who weren't killed were generally enslaved and sold.
Infant mortality was very high at the times," Vassallo said.
True. Of course this was to a considerable extent because parents intentionally killed up to 50% of their children. But it's still infant mortality. All ancient peoples except the Hebrews practiced infanticide. Writers at the time commented on the really weird practices of the Jews, the prime example being that they raised all their children.
I think he’s concluding that because there were but two known battles which had such a level of carnage, and in the second one mentioned, the dead might easily have gone unburied.