I also agree that for the brighter students, it's not 'hard', it's just a question of explaining it, then drilling them on it, same as times tables really. I'm pretty sure I could learn this stuff to pass a test quite quickly.
For the students who are not in this category, I can imagine it being a nightmare.
It is not necessary knowledge though, to me, unless you are going to promote multiple languages in secondary as your primary aim of that stage. If that's where they want to take it, it would make sense. Otherwise it does not, I don't possess this knowledge, neither do any of my cohort, and we all have good professional well-paid jobs which apparently don't require it, even those of us who write for a living.