Those are decoy bodies. Unless GM has changed what they do with their test mules, what you see is potentially not what you'll get in the showroom. It's a purposeful move to always keep you guessing. Like the front end cover might be covering up something they looked at years ago and have no plans of releasing, but covering it up gets people talking. It's even possible they're testing a completely different engine that isn't even designated for the Camaro. Once car could be testing suspensions and the other is testing transmissions or towing capacities...who knows for sure except GM?
It's good they're testing SOMETHING. And it keeps us occupied until the real deal shows up.