Luther had "Table Talk" with the seminary students and university students who tended to spend time at the Luther house. These talks were time to discuss, open ideas, get out ideas and/or misconceptions, even to sometimes play the devil's advocate.
Also, Luther himself did NOT write table talk. What we have our notes written by the students. And, as any student is want to do, sometimes they make mistakes, leave out important words, and of course, cannot express the tone in which the statement was given.
So, all of that said, I'm sure it did come out at a table talk session. But who knows if those were the right words and how those words were meant.