Ok historical consideration and realism influence the game, as said there is no dual wielding (or no double head axes) but it's just influence. It would be crap to talk of historical accuracy, there is no accuracy in this game, and it's a game, Calradia doesn't exist...
There is a special thread in the forum for history, it's off-topic and no matter about the game.
Also Turkey is not a muslim country, it have a religious-free constitution, laws are not binded to the Charia.
Couched lances are fine like they are now, it's still a powerful weapon, but it ask timing to achieve this 1hit-1kill attack.
There is many things that are not realistic in this game, for matter of balance and because of game mechanics. How a horse can walk on a ladder? How a guy can stay in water without breath? How a guy fall from horse without damage? Etc...