I think you're taking a wrong look at this paper. This paper isn't actually about whether or not type 3 societies exist. This paper is about the fact that there appear to be no galactic clusters that show a particularly abnormal, greater, amount of electromagnetic emission than the known standard. Which, actually, I'm pretty dang surprised hasn't been searched for already. Then, in order to be a little whimsical and make sure the paper gets read, (s)he explains where they came up with the idea for this experiment.

Seems to me like a completely rationale thing to measure about the universe. Imagine if the result had come back true?