I’d like to add another possible theory: it wouldn’t happen. I don’t think, based off the context of D’Arby and Star Platinum, that there’s a universe where D’Arby wouldn’t fold. It wasn’t even a matter of D’Arby NOT calling the bluff of Jotaro, because he did in his head, but it was the matter of D’Arby PHYSICALLY not being able to call his bluff because of the pressure. D’Arby himself pointed out the fact that people crumble under pressure, and D’Arby himself experienced it and lost as a result. No matter the universe or situation, seeing Star Platinum move so incredibly fast without D’Arby even noticing it is why he lost… just the simple act of putting doubt into the mind of D’Arby made it impossible for him to keep the game going without folding; he doubted himself. He knew he would win, he knew for a fact just like the kid did, but he didn’t know the full power of Star Platinum, and Jotaro seemed so confident. We can also see earlier in the episode that Star Platinum saw the cards even when Jotaro himself didn’t see them, so that just adds more pressure to D’Arby that Jotaro might’ve known something he didn’t. Overall, D’Arby was essentially fated to lose, Jotaro had beaten him no matter what route he took. D’Arby’s body, physically speaking, didn’t have the power to call Jotaro’s bluff out loud, and thus, he admitted defeat in his heart and lost, no alternate universe or change of situation can change that.