[orf]

> They might as well be two different types

The problem is they are different types, which has huge downstream impacts. Not least of all would be subclassing.

The static analysis you’ve described could work in simple and trivial cases, but the problem you’re now trying to solve is “what concrete type is this object”, and in a dynamic language like Python this can only be fully and 100% determined at runtime.

Mypy and the like do a good job, but often rely on protocols rather than concrete classes. There’s also no impact if the types are wrong or ignored, whereas for this a typing mismatch becomes a subtle runtime issue.