@justanothermanganerd I guess the trope is most for reader benefit, to let us know what's going on. I do wonder why they don't just think this to themselves too. In Saike's case here, saying it out loud will also benefit whoever has to take his place, if he's KO'd.
If Min Min is so good at reading people's movements, then it should be possible to win at rock-paper-scissors. But nope, not even going to touch that, huh? This was stupid.