I don't know why it bugs me so much, but it's "in medias res". There's an "s" on the end of "media" in that phrase. I knew the latin phrase and when I saw it in the WEG Star Wars book spelled wrong I pointed it out. My friends were incredulous. No way I could know better than "professional designers and writers". And yet, I did. We didn't have a name for it back in the day, but that was my first run in with what's become known as the Mandela Effect. WEG repeated the error in the 2E and 2E Revised and Expanded books, along with the FF 1E reprints. At least the REUP people got it right.
I realized quite early that designers and writers are human and capable of mistakes. As a result I don't venerate them or the game rules anywhere near as much as many of my friends do. The designers aren't gods, they're people like you. The rules aren't holy, they're someone's house rules that you paid for.