Let me just say that this episode was needed for the sole purpose of showing off what else Pokémon Connoisseur's can do. Therefore it's not filler.
To be more precise- It's not a filler in between two canon events; Finding out Opelucid Gym is closed in the start, going to Virbank City in the end.
I mean we were going to find more about them eventually. That's for anyone who thought this episode wasn't needed as Cilan got no development.
To those people who do this: Enough with all those unnecessary and mean phrases towards Kotetsu whenever you mention him (by name or not).
We get it, you don't like him, there is no need to keep shoving it in the faces of people who don't mind or like him. And seriously, just get over it.