No we learn new grammar but just not from a textbook. Tbh there's not really anything else to learn at that point other than minor occurrences. And these things are peculiar to particular authors. The best way to learn them is by practice at actually reading them and learning them from practice. The thing that becomes really important is the use of particles but no textbook is going to teach you that satisfactorily since each author uses them differently and so the only possible way to learn is by practice.what? so you just spend year 11 and 12 translating and not learning any new grammar?