Aha. I was remembering hearing the same thing somewhere, and my guess was Fr. Pacwa of EWTN. However, I could not ascertain that yesterday. Do you have a source for this belief? See my 6678 and the antecedent discussion.
I do not recall where I encountered this information about co-habiting after a betrothal.
If I get time to poke about my library and find anything, I'll let you know.