The black stone bundles that drop at Kagtums no longer have the weapon or armor stone tag, but they are still separate items, you can get 2 different stacks of them.  I thought maybe I had a bug so I opened both stacks and went to grind, still had the armor stone bundles not stack. 

*have not tested other grind spots that drop black stone bundles yet*

*have not tested current patch that came out 30.04.2024*