This is UI theory gone wrong. The idea that users will give feedback more freely when something looks unfinished is at best a non-validated theory.
This used to work with actual paper prototypes. But going the extra length to make UI designs look hand-drawn, when the users know full well they are computer generated is just busy work.
Showing the users what the actual design might look like works better and it actually captures important design choices such as shapes, colors, proximity, etc. that users care about.
I have been to many UX tests. Regardless of sketchy design look or not, the user will either have no problem providing feedback or they won't give useful feedback. It mostly depends on the person, not on what you show them.