It's a wonder that nobody else figured out that Williams' knuckleball was fake. Sure, Williams avoided pitching it to Takami because Takami has good eyes, but Tokuchi himself figured it out by watching the ball on video. Which means anyone else could have done so as part of standard research on the opposing pitcher.
Tokuchi is expert at handling the ball spin and on top of it he suspected that Williams's team cheats so he scrutinized every aspect of their play i.e. he was actively looking for evidence of cheating. Other teams studied paths of the ball but they were not suspecting that knuckleball was fake.
Maybe so, but even the dumbest ones on the team know that knuckleballs do not spin. That means anyone who studied William's ball in slow motion for even a second should have seen it spinning and figured that something was off.