Why is it so hard to believe a mostly composite, small, basically race car comes in around 2100#'s? Also, by winning the way they did, I can guaranty that the cars HAD to be weighed after winning. Knowing that, I don't think the weight claims are false. I think it might be a little much to expect the road-going cars to weigh 2100#'s. I also don't remember whether it was specified whether that was a dry weight or a wet weight. (dry meaning no fuel load and sometimes no other fluids as well)
Also, by working around composite parts all day, I don't have a hard time believing that a naked shell would come in around 250#'s. We also don't know what they consider to be the "shell". It could just be the driver's cell. Even at that, we don't know what that is comprised of.
I understand I'm being a major devil's advocate here, but I don't think there's really any justification to call BS on things just yet.