They are using the term unsupervised properly, but do I like your characterization of callling it "coincidental". That is basically the essence of unsupervised learning. We have a system doing something (typically some form of optimization), and "coincidentally" it learns something useful that we did not explicitly tell it.
Had they created a next-move predictor for chess, they wouldn't have been surprised to find a neuron representing the aggressiveness of the player.
It's a good result on its own but the word "unsupervised" is a bit annoying.