Things were tough in the early 1500s as you know, and women were simply property. Promises which are coerced with threat of violence are not valid ~ I suggest you learn to study that period ~ let's say from 1400 to 1600, with a very open mind. Did you know that Jeanne d'Arc had to be accompanied by loyal armed men day and night to protect her from being raped by her own troops? Even with her security guaranteed by the French royal family, men would attack her or any other woman away from her own male relatives just because they could, and most believed they were supposed to ~ else women would just run wild and ruin everything.
That sort of attitude didn't begin abating in much of Europe until the 1600s, but by then the abuse was pretty much limited to targeting 'witches' ~
Was Luther’s consort a nun or was she not? Or is it your contention that she was, on top of that, a married nun? My point is very simple: they were not free to marry. All this piling of historical context is fascinating but it does not alter anything in this simple proposition: they were not free to marry, so they were not married. They were fornicating.