How does literary criticism in Margaret Atwood's "Happy Endings" parallel the social rebellion present in story?

The Atwood "story" does several things at once. 
It is a guide of sorts, a kind of lesson to aspiring writers about how plot works, and about how stories end. Her point, given at the end of the piece, is that plot is simply a "what and a what and a what," a series of empty events with interchangeable details and characters. The only true ending, as she says, is that "John and Mary die."
The examples she uses, the story of John and Mary in all its permutations, lays out in a purposely schematic way the sexual politics of John and Mary's relationship. Mary either allows herself to be used by John because she hopes he will marry her (story B) or because she feels sorry for him (C), but in each case Mary is frustrated because John cannot meet her needs. Neither John nor Mary is very clear on what their real needs might be, and it is ironic and tragic that neither John's ability to act nor Mary's more limited ability to get what she wants leads to any fulfillment. In fact, B and C both end in suicide or murder. Atwood's point is that no matter how you switch around events, the outcome (the lack of emotional connection, or of essential freedom to be ones' self) remains the same.
If we understand this story to be about "social rebellion," then the thing it is revolting against is (I suppose) the petty concern for "plot" and "happy endings" that fiction writers and everyday people are so obsessed with. The details of plot make no difference: it doesn't matter in the end whether John is young or old, or if real estate values go up or down.
Atwood's final line points a way out of this dilemma: in trying "how" and "why," she is calling for action to make real change (the "how") and analysis to understand our current situation (the "why"). She suggests that the true purpose of fiction may be to effect change in these ways.