Especially if you look at the character notes (ch 46.5) I think there's a strong correlation between how good a partner is and how beautifully they're drawn. Idogawa's a special case here because she's drawn with a really plain face in normal clothes, so there's a sharp divide between her appearance with and without competition makeup that isn't present for any of the other elite-tier partners in the story. I wonder if this is a visual representation of the fact that she's not really rated by the audience and reporters (to the point where the reporters can't even remember her name, ch 40).