Actually, I think you've noted a significant issue: Pony looks to have been designed, at least in part, based on a sound theoretical foundation provided by mode

Actually, I think you've noted a significant issue: Pony looks to have been designed, at least in part, based on a sound theoretical foundation provided by modern type theory, semantics, etc. However, the documentation does not use the standard terminology of these fields. As a result, it is difficult to evaluate some of the claims that are made.