As far as i know, the additional 100 calories on their own shouldn't induce a metabolic effect like increasing fat oxidation by up to 40% and reducing carb oxidation. Adding 100 calories into the control would be nearly impossible to skew the metrics they were investigating.

Since you're a researcher, is the washout really irrelevant as the other guy says? None of the changes the participants would've made during the washout would have increased fat oxidation and they weren't restricting a lot except colorful foods basically. Since they were required to provide food journals they could be accounted for, and even if they did eat some anthocyanins without reporting, why would the fat oxidation rates increase that after the powder was given? Wouldn't the increase have been lower or non existent if they still consumed large anounts of anthocyanins during the washout?