I disagre! This is the best possible reason and justification to use the Elfternship to train Branarhune.
As I, on the contrary, want to complete Branarhune with the help of Elf swordsmanship.
Especially if/because they are skillful and speedy swordslingers!
In fact, that would be perfect for completing Branarhune -- because we would have the perfect target to practice on. I mean, do you want to practice Branarhune without a supernally swift and agile opponent to test it on? Or would you rather complete it by having those sparring partners?
I mean, think of it this way -- this way, we can set Elves as the speed/dexterity/agility/skill benchmark for Branarhune. Otherwise, who are we going to use? The Ulricans at Ulrikadrin, or the Undumgi or Gunnars again? Ourselves? A trainer hired via the Colleges?
Plus, it pleases me to have Mathilde pick up the sword from human teachers, learn more from dwarfs, and even learn from elves too. Having learned from multiple races and traditions of swordsmanship? That would be great?
We could hire a trainer from the Colleges. In fact, if the Colleges can get us an Elf swordsmanship trainer, that would be great, and I would rescind my "Nooo! I want to learn from the Elves, for the trickstery and anti-speedster/anti-skill sword style!" wailings if we could do that.
But otherwise, I think the Nagarytheans would be a perfect oppotunity to round out and complete Branarhune.
I mean, just... It just makes perfect sense to me. You go there to fight alongside them in the war. And they will help teach you how to fight Druchii. And as part of learning how to fight against Druchii, you'll pick up Elf swordsmanship, and anti-Druchii techniques, and with that you will achieve grandmastery in the sword.
It's just more meaningful and dramatic that way to me, y'know?
It makes for more of a story that way; "I went to the Elf isle of Ulthuan, to the kingdom of Nagarythe, and there I finally completed my swordsmanship skills!"