I did that for a stay in November for which I still have not seen anything on my Miles & More account.
This request was forwarded to Marriott I guess, because the answer was something like "Sorry, refused, because according to Marriot the points were already posted to your hotel account."

Well, yes, in my Marriot account the points related to this promotion already posted a few days after my stay. It's the M&M points that I want...