The notion in the head of the teacher who believes students learn a fl through rule-getting and rule-using is that they first learn a rule, then they practice applying the rule. The teacher assures himself that they have learned the rule by asking students to apply the rule on a test. Once the students have shown they know how to apply the rule, the teacher spends the rest of the time getting the students to practice the rule, i.e. use it over and over so it becomes engrained as a habit.
This is a combination of the old model from structural linguistics and behavioral psychology along with cognitive psychology. IOW, it’s an amalgam of two wildly opposed conceptualizations of how the human mind learns. It’s a mish-mash.
After a successful final exam, students are presumed to go forth and use the TL. They don’t, of course, and that is ascribed to “the fact” that most of us don’t remember everything from our math or history classes, or to “the fact” that languages can be learned well only by very bright or very talented persons or that no one can learn a fl to any level of proficiency without living in country for a period of time. Excuses all.