I am just making a wild speculation here, with no experience or industry knowledge to back any of this up (so someone with more brains might be able to correct me) but I would guess it matters what Caterham is doing because the DMV don't want folks buying a C8.R Le Mans Corvette body from GM, then going to Callaway to buy a juiced up LS-drivetrain, then a local shop to do installation, and then claiming SB100 exemption for their new Corvette.
But I'm probably way off base because of other details of SB100 I'm not familiar with. Still, it was fun speculating.