Items on the floor don't overlay in OXC/OXCE.
Only one item is ever rendered.
In OXC, it is always the heaviest item.
In OXCE, it is either the heaviest item, or the first found corpse item, or just the first item... depending on how many items are on the floor... to speed up rendering.
PS: you also don't see all your 100000 weapons rendered on the weapon pile in your craft, only one of them is rendered.