Well the questline is called "The history of The West" and it somehow follows the development stages of the game (Poker -> Pants -> Forts so on). Dueling has always been a part of the game, including it would've been kinda awkward.
Dueling has always been part of the game you say.
The quest is "The history of the West" you say.
Surely then logic dictates that something that has always been part of the game should be part of the celebration of its history, no?
I understand the reasons for not including a duel Anny, I get that, so maybe it should have been an either or, a decision tree.
To complete this quest you could
(i) complete on forr battle, or;
(ii) complete one (or more) duels
Then forters don't have to duel and duelers don't have to fort.
But as usual, the emphasis is on one part of the game, a part that fort attendance proves is not all it used to be.