>>55523973If it takes place after XY, unless it's so far in the future that the details were lost to time, then that raises the core problem of "Okay, so who was the kid who thwarted Team Flare? Did Lysandre want to make everyone immortal to preserve the world's remaining beauty forever, or kill everyone except his elites so they could begin restoring the world's beauty with a clean slate world? Did that kid catch Xerneas, or Yveltal?"
GameFreak doesn't have the balls to fully cement another protagonist as definitively canon because that could upset the opposite gender, and especially not the balls to definitively canonize a version because that effectively means the other version is the "wrong one".