"Unlike their flint counterparts, the basalt vessels were not made at homesteads, but in central places of manufacture. The vessels were then transported to settlements, said Rosenberg, based on a paucity of production debris at dwellings’ excavations."
S.C. My Thoughts:
1) When handling an object it is helpful to have something that assist in your grip. I suspect the cross hatch provided hands a surface that helps in maintaining a persons grip. It functions like cross hatch on a piston handle.
2 If they had a machine or machines that allowed them to partially hollow out the vessels which would explain the "Factory". Takes some time to fabricate that machine and they might try to keep it "Secret" so that other manufacturers would duplicate the factory and compete with them.
Here is a much later ancient india lathe for soapstone columns and pillars.
Hoysaleswara Temple Famous Lathe Pillar. (10th century AD)
