As I said you should search and read those threads. Nobody there had actual marriage documents , they were symbolic or religious ceremonies that did not produce legal documents. Yet, they were denied because there were “too married for a K1”. Im not here to argue the wording of what constitutes a marriage, I’m aware of that. However, I’m also aware that there exists those denied cases as I’m also sure there many others who managed to bypass the interview with those unofficial ceremonies as your friend did. It all comes down to if you want to take that risk, this is your immigration journey. Im merely informing you of what I have read here on VJ.
To add to that, as someone who did K1, I would definitely go with a CR1. They both take 2 years so why not choose the superior option if they take the same amount of time?