Using the Negative of Language Versus Pseudowords to Map Out the MD Network?

In this study, you have a written language comprehension localizer. So it's listening, it's reading sentences versus reading lists of pseudowords. And interestingly, you then use the negative of that contrast to define the multiple demand or MD network. Isn't that weird that you can map out the MD network quite effectively using the negative of language versus pseudowords? I don't know if it's weird. I just think it's a weird thing.