Butt they're going up and down, not side to side, which is supposed to be thinning. Side to side is what makes people look bigger. I like the outfits :3
Wide stripes also make people look bigger, and those are pretty wide stripes. BUT I agree, I like the outfits too. It's nice to do something simple and chic sometimes.
What I don't like is everyone's hair. They should have done something more exciting with the hairstyles since the outfits are so plain. Sakura and Masaki especially look like they just rolled out of bed and pinned back their bangs.
Maybe that's the point of it? The hair. It's so simple, just like the outfits. But we still have Ai no Gundan's outfits to look forward too, hopefully they're more colorful for some contrast.