The types for a lot of girls are rather arbitrary. I've given up trying to figure out the system for determining why certain idols are classed the way they are and accept that most of them are based entirely on whim.
My theory (well, headcanon) is that the idols themselves, largely, select their types; this is taken from a comic -- which I can't seem to locate right now -- in which the Positive Passion girls are talking, and the conversation turns to why they all chose to be Passion-type idols. Mio says something about wanting to be sexy, and Akane says something about her hot-bloodedness. Aiko, on the other hand, is trying frantically to think of an explanation that doesn't reveal that she thought the option read "Fashion".
^Then why aren't Kirari, Shin and Chizuru cute? Their goal is to be cute idols.
Cinderella Girls Theater
劇場第1271『石川に来ました!』
Theater Episode 1271 - We came to Ishikawa!Talked about this when they had a live show here beforeSeems we have the same source of infor-mation~I know it from Aa-chanI know it from Nono, but... Uzuki, you know Kanazawa dialect from Miho and Kyoko, don't youCorrect... Whaaat~!? You two are amazing! Did you study for this?When some-thing is fresh and livelyNamanama.Namanama?
Huh, that was fast... Okay, Rin-chan, what's 'kitokito'!?When a snowy road is slipperyWhat does 'kinkan namanama' mean~?I'm getting a major 'get them before they get you' vibe here~Okay, readyFor this, Uzuki Sensei has prepared a Kanazawa dialect quiz for you two!So, Ishikawa Prefecture!...It's as my little sister says. I'm the big sister Nagi. Not negi (onion), and not kugi (nail) either14 years old, 2nd year in middle school! Hayate Hisakawa~! And this is Ha's older twin sister, Nagi♪Rin Shibuya here, today we're in Ishikawa to introduce these newcomers