Well, it's actually too grand for a gym and too flashy for a secret base. It probably has something to do with the League.
Now that the Fairy type has been confirmed and we have some examples, we can start to speculate better than before. This list includes all of the 'reasonably possible' fairy type Pokémon changes. Japanese fairies aren't always 'soft, pink and cuddly', but can also be mischievous, mysterious, and powerful, explaining why Absol, Zoroark, and Whimsicott are in there. But they can still be graceful, pretty much including anything with the ability 'Serene Grace'.