I didnt know this episode had only 1 gym, i tried to read as less as possible of it.
Btw I dont think Saphira would bring those megas since Ame said Noel was the only one who uses a Pokemon that is not of his specialist type , and mega altaria had been already used so for this i guessed M Salamence. And y i also thought about Hydreigon Salamence and Garchomp question, but imo, since we r speaking about the last gym leader, her team should be very strong, so why don't use them, there is not only 1 deino/gible/bagon in pokemon world.