The "apex of humanity" comment is about how Ciel using magecraft and Idea Blood can make an attack that has the mystery of Excalibur. this is a statement about her magecraft not the powerlevel although I wouldn't be surprised if the powerlevel were comparable considering what it actually was shown to do(it's her 3rd ascension NP by the way).
And while It's probably impressive I'm going to guess the Idea blood plays a bigger role in that level of mystery than her alone.