It seemed to me that the "beautiful propaganda" as you call it.. and I can't really disagree with you.. could be an olive-branch extended from the SK film industry to NK audience (because we know NKs smuggle and watch SK dramas.. even a soldier in the show does that).
So idk, I like to always approach things pessimistically AND optimistically.. then compare the two perspectives. In this case you're the critic and I'm devil's advocate.
Will it make a difference on the large scale? No. Will it delight and sway a few NK citizens toward reunification? I'd guess probably. But who knows.
Of course. Because as we know, every positive event in history has occurred while holding hands and respectfully requesting what was required.