The OP said that looking at the landing grid layout some of the affected pins were ddr0 and ddr3. Unless the affected pins still managed to make an electrical connection I doubt the cpu could've passed the bios post."Tested Working" is a pretty loose term. Even with the damage it could be at least partially functional as long as none of the affected pins were critical. Maybe all the seller did was check that it boots to bios, or the damaged pins are for the igpu or some other unused portion.
