I don't think you can really blame GM for the absence of a C7 Corvette kit from Revell. If they paid licensing fees and have a green light to produce a kit, they really don't need 'detail specs' from GM.
If Revell really wanted to get the kit on the market, they could borrow or rent a C7 and do their measuring and photographing just like they do with out-of-production vehicles. Or, a real car guy at Revell could buy a C7 to use for the kit engineering . . . and write it off.
There's more than one way to skin the cat.