Is the Model 3 just a cheaper Model S by the same argument?
(It's a genuine question. Yes, the Mustang was based in part on the prior Falcon platform. Wouldn't Tesla sensibly base the 3 in part on the S in the same way Ford continued to sell the Falcon alongside the Mustang? If Tesla is sharing literally nothing across models, that seems like a non-sensical way to run a car company to me.)
They're sharing what they can obviously, but the platform will be different. There are a lot of cars that are like 90% similar, especially sedans and crossovers sharing the same platform. To that extent, the Model X apparently used the Model S platform as its starting point (but no idea if it's still shared). The Model 3 however is a mid-sized sedan compared to S's full-size, so the sharing would mostly be limited to tech and components, but not platform.
(It's a genuine question. Yes, the Mustang was based in part on the prior Falcon platform. Wouldn't Tesla sensibly base the 3 in part on the S in the same way Ford continued to sell the Falcon alongside the Mustang? If Tesla is sharing literally nothing across models, that seems like a non-sensical way to run a car company to me.)