Yes, but there are two templates called 'SKEL_Human_Skull_A' and 'LOOT_Skull_Human_A' that share the same visual resources, physics, icon and stats. Most of the time the first one is used but a few items have the second template, so they don't stack. 'SKEL_Human_Skull_B' has different resources but shares the icon with the templates above, yeah, so most people won't recognize they are different when organizing their inventory.
If that is the reason, so that they look and are described the same, but somehow are not really the same, I would say, that is pretty bad game design.
Players don't see the templates, they only see, that stuff seems to not get properly stacked and get annoyed, like me and my friend.
It just looks ridiculous and buggy:
https://gyazo.com/d817604065445e1a0c40f0976bd9acd3
