Yes, maybe the winner should just start the thread then and people come in to ask for a critique.
I thought the winner simply because we're all happy when they are announced, we cheer and congratulate them, everyone is in a good mood.
And when they open it, people won't be as inhibited when pointing out the good stuff they liked (could be X for one, Y reason for another). Then they return the comments, more people join in and talk about other stories, and the ball rolls.
Of course, it isn't just so we can all feel good and have a cookie, people can ask for feedback on any aspect of their stories. And of course, people may know by themselves what they could've done better, don't want it public, are not interested this month (but may be in the next), etc.
But maybe by creating a structure (the winner opening the thread, in this case) it would eventually become a regular thing, so in time there would always be one, whether a certain month spikes huge interest or not, and it wouldn't depend on one or two specific members to keep critique threads rolling.
Just thought the winner of the month could be this "beacon" for the reasons I mentioned earlier.