International Relations (noted in the article) also sounds like a degree that would be popular for pre-law.
My guess.
Skimming the required courses for the prelaw program my college offers, the requirements for that are much more aligned with what's needed for a polsci degree then an IR degree. Theres only two classes from prelaw that overlaps with the IR requirements and one of em's not even being offered anymore. Also, the polsci half of the department offers scholarships aimed at prelaw students specifically. (Technically Political Science and International Relations are the same department here, though they have pretty different requirements and different people in charge of the programs)
To generalize the courses, polsci is more "American political science meets history meets business with a dash of criminal justice" while IR is more "Global political science meets history with dash of anthro".