Fountain of Knowledge

It is an interesting question about the plot. Different authors seem to have different approaches, but I would say yes. Part of the difficulty is that since the story feels so absurdist, authors get away with skipping elements. My guess is that over time, bizarro will either drift further away from sci-fi and fantasy or will start having more guidelines about plot.

After all, there are plenty of sci-fi writers and fantasy writers who want to pose a cool situation and skip the plot. They just don't get published much. Writing bizarro without a beginning, middle or end would seem to lead to the same thing.

As for metaphor and symbolism, I think they are often used, but sometimes there is a meta-symbolism in that there is a feel of metaphor or symbolism, but it is no more easily pinned down than anything else. Do that well, and you have very good bizarro. People will struggle to figure out what you mean, and will have to remind themselves it is bizarro.