i think you're missing the difference between duelling and training.
duelling is a game in it's own right, not training for battle. It's actually rather bad training for battle, considering duelling/ advanced blocking ability on battle is rather worthless.
I think its you whos missing something here...
Duelling actually just means a 1v1 fight, which can be for training or competition and is the best way to practice melee fundamentals. And dueling is actually GREAT training for battle, it's where a lot of players learn how to block AT ALL, let alone have "advanced blocking ability".
And how the hell are duelling skills not important in battle? Blocking, footwork, and timing, and knowing your weapon is what every meleer needs to do well in battle, and all can be learned from dueling.
edit: I was actually a native player for a long time till i tried crpg, and I still go to native duel servers often. Your view on dueling is quite close-minded...