Yeah that would be amazing, but sadly nobody has made that work for any CAD of reasonable complexity.

In reality, CAD version control is done just like assets in the artistic world (game design, animation, films, etc): with file locks.

I used to work for Dyson. There's no way you're designing a vacuum cleaner with code-based CAD. We used TeamCenter (which is probably the worst software I've ever used, but for unrelated reasons).

I mean, the CAD software, even though visual, has to retain some internal state of the model, right?

It's possible, but I don't think there's enough pressure for these companies to support exposing that state to the user.