When they say “graveyard,” they mean “trash pile.” Every any colony disposes of their waste away from the colony, and many will have a specific place they dump it. They throw their dead in the pile along with everything else that they need to remove from the nest.

As far as having an understanding of what’s in the hole? Ants do not understand like that. They instinctually follow pheromone trails but don’t really think about it.