Random, but Wailord's page appears to be incorrect. It is currently listed at 7-A because it apparently "swallows schools of Wishiwashi whole", and seeing as the Solo Form of Wishiwashi is "Below Average Human", I'm assuming the implication is that Wailord swallows Schooling Form Wishiwashi. This does not appear to be the case looking at the Pokedex.
Wailord dex entry in Pokemon Sun:
Wailord pursue their prey in pods. With their large mouths, they can swallow entire schools of Wishiwashi whole.
Wailord dex entry in Pokemon Ultra Sun:
They eat so many fish Pokémon that when Wailord become too numerous, fishermen have to chase them off.
The Alola dex entries for Wailord demonstrate that the defining traits being emphasized are Wailord's huge mouth and volume of prey; that is to say, opening its mouth to consume an entire school of fish in one bite. Wishiwashi 'schools' do not always refer to the powerful form of the same name, and can be and have been used to refer to a typical gathering of Wishiwashi.
Wishiwashi dex entry in Ultra Moon:
Called “demon of the sea” by some, when Wishiwashi are injured in battle and their numbers dwindle, they become a regular school.
Schooling Form is also called a 'formation' by the Pokedex, indicating this is not just the result of schooling, but of the Wishiwashi coming together
and assembling into the Schooling Form.
Wishiwashi Dex entry in Ultra Sun:
Wishiwashi assemble in this formation to face off against strong foes. It boasts a strength that earned it the name “demon of the sea.”
New Pokemon Snap also
directly depicts Wailord attempting to swallow a school of Solo Form Wishiwashi, then being chased away when they assemble into the Schooling Form. Subsequently, I think Wailord scaling to Schooling Form Wishiwashi is... not accurate