so to answer NN's question "Why?", one of the animators fukuda_keitatweeted about his conversation with his producer
P: lets have a NN eyecatch in her race outfit K: Didn't we have her already in Season 2? P: Yes, we did K: hmmm.... K: her cheer outfit is technically a race outfit P .... K ....
Huh...? Huuuh?! W-what? We're in the middle of a very serious scene right now, right?!So what have I suddenly become the eye catcher?! And in this outfit no less?!I don't understand!?