Agreed, it is dubious. Case in point, whether you believe the Aptera is a "real" car or not, they did develop and bring to market a high demand, safe vehicle from the ground up without billions of dollars. Or, an even better example, Tesla has already done it once. If one wanted to point out Lotus' involvement in the development of the Roadster, I still point out it didn't take billions of dollars.
As far as the comment that Tesla intends to do it all "in 30 months", what do you think we were looking at on March 26th? Something Elon whipped up in his garage the night before? They've already invested years of development in the Model S.