IMO a critical feature of the Turing test/imitation game, which many modern implementations including this site's linked paper ignore, is that the interrogator talks to both a human and a bot and must decide that one xor the other is a human. So fooling an interrogator means having them choose the bot as human over an actual human, not just judging the bot to be human (while probably judging humans to be human even more frequently).
When the interrogator is only answering "do you think your conversation partner was a human?" individually, bots can score fairly highly simply by giving little information in either direction - like pretending to be a non-english-speaking child, or sending very few messages.
Whereas when pitted against a human, the bot is forced to give stronger or equally strong evidence of being human as the average human (over enough tests). To be chosen as human, giving 0 evidence becomes a bad strategy when the opponent (the real human) is likely giving some positive non-zero evidence towards their personhood.
When the interrogator is only answering "do you think your conversation partner was a human?" individually, bots can score fairly highly simply by giving little information in either direction - like pretending to be a non-english-speaking child, or sending very few messages.
Whereas when pitted against a human, the bot is forced to give stronger or equally strong evidence of being human as the average human (over enough tests). To be chosen as human, giving 0 evidence becomes a bad strategy when the opponent (the real human) is likely giving some positive non-zero evidence towards their personhood.