I'd give them the benefit of the doubt here, it's been known that there is a day one patch, why would they waste their time doing all the performance testing on the base game, if the patch is supposed to bring improvements?Hmm, I'm skeptical of that reason, I would hardly describe Hogwarts as a "broken game" not by a looooooooooooooong way.
What we don't know is if reviewers get early access to the patch, so they could have already done the testing with the patch, but just on embargo until the game fully releases.