Don't ask me why, because that's what the credit system says. Your tuition is credits, and each credit includes a certain number of hours (one credit in our school is 18 hours). Before the implementation of the credit system, the tuition fee was paid for one academic year, so you can take classes in this academic year at will.
Similarly, before the suspension of classes, if you finish the course within four years, you will not pay any money, but if you don't finish it within four years, you will have to charge tuition fees for one semester or one academic year (different schools) according to different schools. Knowing that graduation has been completed, of course, most schools can only postpone graduation for one year and drop out after one year.