The core thesis is that your types received by the api should not be the same as the types you process internally. I can see a situation where this makes sense and a situation where this senselessly duplicates everything. The blog post shows how to do it but never really dives into why/when.
Personally, I think that's a good idea. Design patterns naturally make sense (Visitor, Builder for e.g) once you encounter such a situation in your codebase. It almost makes complete sense then. Otherwise IMHO, it's just premature abstraction