.001 for creatine levels isn't surprising; that's a lot of creatine. I'd explain the cognitive tests with the practice effect, because it is unlikely that creatine had such a massive effect and we only discover it now.
What I worry about more is that it has more to do with fixing a deficiency. That being deficient in creatine causes a cognitive loss more than supplementing causes a boost.
Also IMO, the Balmer peak is a stronger effect than creatine.