I’m just speculating here, but couldn’t it be to prevent the looting of a country’s national treasures?
Nothing I’ve seen yet suggests that the items were stolen from any rightful owner. Only that they were “mislabeled” on a customs form. It doesn’t strike me as mislabeling if they were described as “tiles”. They’re clay. They’re fired and hardened. Would “tablets” be better? But they’re not whole tablets. They’re fragments. They’re... Tiles.