I think Luna said that she didn't trust the official release because the romaji for vortex is different.
It's normally BORUTEKKUSU for Vortex.
But Build's finisher name is BORUTEKKU. It's missing the S at the end.
However, if you type BORUTEKKU into google translates, it does say Vortex. But you have to remember Google translate isn't a dictionary. So she's thinking that whoever made the ad, just did a lazy google translates on BORUTEKKU which is why they wrote down Vortex. If you actually look up BORUTEKKU on Google, you don't get any results that say Vortex.
But if you check an actual dictionary, it autocorrects it to BORUTEKKUSU with the s:
http://jisho.org/search/%20%E3%83%9C%E3 ... F%E3%82%B9