The fracturing is clearly from a sharp point from underneath the core. That sharp point to the left is a clear indication of a pressure point which caused the fracture. I've got some old Tbirds on the shelf and could pretty easily test the theory.
Edit: Okay, the pressure was from under the core, but above the ceramic. It looks like a scoring mark along the edge of the core, like a flat screw driver was used to remove the core. This guy clearly stabbed the core with a pointed object, probably a flat screw driver by the fracture point. The reason he got fairly clean breaks, except in the middle, was because he had the processor in the socket when he crushed it.