I'm not understanding something about the Mion/Shion thing

https://preview.redd.it/0qftade9o7ng1.png?width=1920&format=png&auto=webp&s=f8d4442a3a0653f4210ed3a12babf34216f5812b

So until this scene I thought that Mion never pretended to be Shion and it was Shion he was speaking with in the diner the whole way through, but the conversation here seems to imply that the one who told him about the Dam Project after those thugs attacked was Mion. What's going on?

Is it mistranslated, did I just misunderstand something or am I supposed to be confused here?