Post-modernism tends to be a catch-all term that encompasses too much to be truly meaningful and also varies from art to art.
However, a few good examples can be given.
One of the icons of modern architectural post-modernism is The Sony Building (formerly the A. T. & T. Building) by architects Philip Johnson & John Burgee.
Why? Because it was a response to the dictates of modernist architecture.
The modernists were themselves rebelling against the fussy detail of Victorian-era architecture. Like all good doctrinaire rebels they refused the obvious route of saying, do whatever you want, and indulged themselves with a plethora of rules that had to be followed to the letter or you were kicked out of the club. An absence of frivolous details was a prime rule, combined with blather about function being beauty and the like.
It turned out, to their total surprise, that people, the common, ordinary people they were purportedly designing for, loved detail. Loved fussy, frivolous, unnecessary detail. Whoda thunk?
So when Johnson & Burgee designed the AT&T building and added a frivolous, totally non-functional Chippendale-style, broken-front roof pediment, the architectural world went bananas. Everybody else said, meh, but it opened the doors so that architects could ignore function and add frivolity just for the fun of it.
Let’s try a different medium.
Superhero comics are totally modernist. You need a reason, however idiotic, for the superhero to come into being. You see this reflected in movies like The Matrix, whose world is run by human brains being used as computers. Idiotic beyond belief, but completely within the modernist world of function.
True postmodern science fiction films ignore this and just set up their worlds without regard to rules or reason. Think Being John Malkovich or Eternal Sunshine of the Spotless Mind.
So when you claim that “post-modern storytelling demands a certain level of rationalization for every event that occurs” you have it exactly backward. Post-modern storytelling doesn’t require any reasons. The story is all. The ending of The Illusionist is pure modernism. So is the ending of The Prestige, which is hardly surprising, since it is taken unchanged from a book by a noted science fiction writer, and science fiction is the primary literary expression of modernism in the sense of rules and reality. (The sense of modernism for radical experimentation like Eliot and Joyce is an example of how the meanings of these words are so skewed when applied to other arts.) Post-modernism takes the rules and jumbles or subverts or ignores them, just for the hell of it. This makes it totally incoherent as a movement, but we can identify examples when they are obvious.