I wonder if Diantha and Lance were supposed to be at the Battle Tree but didnt make the final cut or were hold off for Ultra Sun and Moon

After you defeat Dexio at the Tree hs says

>"Terrific! I hope you'll put victory and defeat on the line against the Kalos Champion!"

Its pretty obvious Dexio is expecting the protagonist to battle against Diantha at some point but Diantha isnt present at the Tree, she also isnt in Alola at all and obviously we're not going to visit Kalos. Then why Dexio would say that?

Another one is Lance and here's what Kukui says about him (when he says about his Kanto adventures)

>"And then that last guy, that Dragon user in the cape..."Oh sorry! Enough about me—let's get you in there, yeah!"
I guess you could say its just a throwback but its weird how Johto has no representation at the Tree and Kukui never finished his story. Its like the game was supposed to have a cutscene where Lance and Kukui meet again or where Lance meets us and says he remembers Kukui.

To me it looks like Diantha, Lance and maybe few other people were supposed to appear in SM but for whatever reason they didnt. Is it possible they were held off for Ultra Sun and Ultra Moon?