Categorisation is human trait
Over the years I have worked on many systems where the client wants to categorise something.
Generally it works for man made objects, however like all things there are exceptions (is an infrared lamp a lamp or a heater? It's technically both people don't like this)
If you look at the planets each on is unique in some way, but we just like putting things in a box.
If you work extensively with logic you begin to realise that categorisation is a cognitive thing rather than real. You can write the same program in procedural, object oriented, functional and protocol oriented paradigms they are all isomorphic with each outer it is just a different way of categorising a problem.
Personally under the dwarf planet definition I would shove Mercury in there as it so close to the Sun that the Sun clears the region (it also almost cleared out Mercury as it used to be bigger, like Pluto).
So it is just a putting it in a box exercise, driven by administration not science. Light used to be just a wave in the 19th century until the photoelectric effect was discovered and Einstein screwed it all up with the photon :)