It is also the case that every certified plane I know of, low wing or high wing, will perfectly happily go into a spiral dive if you take your hands off the controls. I don't think any of the high wing ones have long term stability in roll. Maybe some floatplanes are different?
All certified planes have short term (small signal) stability in roll, and all have long term stability in pitch (phugoid should decay within X cycles). Otherwise, they would not be practically flyable by a human, for any length of time.