Sanderson is an awesome guy, but I cringed when I read this essay. Of course, its not really his fault that he got stuff wrong, because post-modernism has become a trendy phrase that 90% of the people using it have no real clue what it actually means. Sanderson seems to be using the TVtropes version of the phrase, which is not what the literary version of the phrase is about. The big problem may just be that he confuses post-modern methods for post-modernism itself.
Sure, the post-modernist is known for using various methods involving playing with audience expectations, doing experimental stuff, lots of weird humor, etc. but what this misses is that they aren't post-modern because of the techniques, but because of the motive for the way the techniques are used. The post-modernist is a person who through whatever bizarre process actually believes the self-contridictory phrase "This statement has no meaning", and take it at face value. Thus, the methods of playing up self-contradiction for irony, of messing with expectations, of any the other tricks they are fond of are a coping mechanism, to help hide the sheer stupidity of that belief that is at the core of their understanding.
Even if one were to simply refer to the techniques when talking about post-modernism, and to just say that this is what they mean by post-modernism, that person would still be making an error. Much of the "post-modern" techniques have been around for over a thousand years, so it is a bit misleading to say that one is post-modern just because one uses these techniques.
Brandon's writings are not post-modern. I would not enjoy reading them if they were.