>Pokemon anime directors state that if Ash wins a League Championship, the Pokemon anime would end

The Pokemon X and Y famously unceremoniously ends with Ash losing the League, despite the entire anime focusing on this eventuality more heavily than any previous anime. Normally this could be attributed to the anime's typical seasonal reset, however, the very next season of the anime resulted in a dramatic format and style change, and Ash DID go on to win the championship, leading into a soft reboot with in the following season.

Why did Pokemon X and Y not end with Ash winning the league, if a format change was already in the works? Was the dramatic format change the anime underwent post-Alola initially planned after Pokemon X and Y, but simply delayed for one generation?