Earlier cybertruck prototypes were built either in Tesla's own prototype facility, or by a company that specializes in constructing prototypes. They claim this

Earlier cybertruck prototypes were built either in Tesla's own prototype facility, or by a company that specializes in constructing prototypes. They claim this one came off the assembly line. That's a pretty squishy claim at this point. I guess we can trust that the car was finished under that particular building's roof. But they sure didn't show it being built.