This isn't about CW doing anything to the comments or the history. This is about the five minute edit grace period
Timestamp of the the question in question: 18:34:41Z
First answer timestamp: 18:36:19Z
Between the first post and the end of the grace period we have about one minute and 38 seconds. Magical time. Time enough inside the five-minute window to change the original question post. It may have been switched to CW in that time, but it's also possible to change the entire bulk or title of the post as well.
And we can then deduce that it was Professor Plum in the library with the wrench.