Sonic Boom
@JohanSSB4 Twitter
It could be that Goh's and Chloe's plots got wrapped up this "early" because this section after Leon is being reserved for falling action after the climax. Something to happen for Ash so that he doesn't fall into the same top-of-the-mountain trap Leon did.
We still have an Isle of Armor left unexplored. Maybe Ash goes there next at Leon's insistence and Ash gets smacked down by Mustard? Bonus points, Mustard beats him with an Urshifu he just recently hatched and raised from a Kubfu, providing a direct parallel to Ash's star Lucario. Mustard would stop the angst character crisis before it gets started and psych Ash up for the next adventure.
We still have an Isle of Armor left unexplored. Maybe Ash goes there next at Leon's insistence and Ash gets smacked down by Mustard? Bonus points, Mustard beats him with an Urshifu he just recently hatched and raised from a Kubfu, providing a direct parallel to Ash's star Lucario. Mustard would stop the angst character crisis before it gets started and psych Ash up for the next adventure.