I think it is meant for students for whom learning English is the main, or the only focus of their college program. Probably because that's the easiest thing to

I think it is meant for students for whom learning English is the main, or the only focus of their college program. Probably because that's the easiest thing to abuse for the extended stay in the US: if you're studying hard subjects, like, say, Mathematics, then you need to put in a lot of effort to pass your exams and stay enrolled. When you're studying English, after two years it becomes easy, so you can stay enrolled, but spend zero time attending classes, just show up for the exams every few months.