Why lillie doesn't stated cosmog?

In the game, we know that lillie in the game has cosmog at start, but when the group discuss this "unknown species" she called it nebby instead of cosmog even japanese stil cosmog, but why lillie just say nebby instead of cosmog

She called it Hoshigumo-chan, Hoshi = Star Gumo = Cloud. She only articulated what she though the pokemon looked like... and it ended up being it's name for the time being, they don't know its species yet. It being Cosmog...

In the game the AF had Cosmog already, in the anime Ash discovered Nebby. No one has info on Nebby so hence the change.