The facts are the facts but the facts that you present do not address the question:
On this DG there is a long standing definition of a proper golf swing which is pro quality impact position. So the question is will a person with poor impact position develop pro quality impact position using MGS?
You learned correct impact position using the Bertholy method so your particular case is not valid to answer the question. I am curious as to what you think the answer is though. Do you believe that MGS needs to be 'fortified' with Bertholy or is it sufficient on its own for a novice to develop pro quality impact position?