It's pretty surprising to me that the mistranslation made it through. It's not like it's a random rule, the correct interpretation is clearly pivotal to the conclusion of this arc so anyone that read the source would presumably know immediately that it was wrong.
In fact, I got impatient and read the next part in the manga to see if it's worth my time. A little bit of BS in the solution and a fair amount of luck in how the rule was interpreted that lie had already been ruled true and theres no reason to be certain that it could be overturned. Basically a double jeapordy issue could have arisen and caused shiho to lose. His logic for not exposing the traitor earlier makes no sense. He just as easily could say anything destructive outside of the game, it's not as if the papers were the only way to reveal a secret. Also his "extra layer of security" with the nametags was pointless. Yes, there is no upper limit on papers, but there is a lower limit, and it only ever went above the lower limit (one per person) after he had figured out the traitor. The traitor not being motivated by money could have also just given up the nametag and lied anyway not caring that they might incur more debt. We even find out the traitor isn't motivated by debt. He also got lucky on other people writing secrets when he was checking and the real traitor knew things about shiho that "should" have been impossible. If they'd had the same level of bullshit information on Yuuchi, he would have been out of luck. I did notice the two girls not having nametags in episode 5 but I didn't think about using the papers to write notes, so I guess they got that over me. Their rhetoric that this line of thinking is "evil" is a bit of a stretch though.