No she didn’t that’s your BIG LIE. Read the whole quote, and read it WITHOUT inserting your ASSumptions:
“Is there a certain amount of very sophisticated mythology that you’re trying to work in here?
There’s - I’m not trying to work it in, but... If you’re writing a book that, I mean, I do do a certain amount of research, and folklore is quite important in the books, so where I’m mentioning a creature or a spell, that people used to believe genuinely worked - of course it didn’t [PM: in her opinion]- but, you know, it’s still a very picturesque and a very comical world in some ways - then I will find out exactly what the words were, and I will find out exactly what the characteristics of that creature or ghost was supposed to be. But I hope that that appears seamlessly. Children often, often ask me how much of the magic is in inverted commas “real” in the books in the sense that did anyone ever believe in this? I would say - a rough proportion - about a third of the stuff that crops up is stuff that people genuinely used to believe in Britain. Two thirds of it, though, is my invention.”
She just gives a thorough answer to the question, the topic isn’t “turned” to magic, the topic is mythology and folklore in the stories. Magic is part of mythology and folklore as well as the occult, in fact that’s why cultists like to wrap themselves in mythological trappings, it gives them the appearance of antiquity which helps them hide their BS. But since the question is about mythology then the magic in the answer would, logically, follow that context and be mythical magic not occult magic.
“Children often, often ask me how much of the ***magic*** is in inverted commas “real” in the books in the sense that did anyone ever believe in this? I would say - a rough proportion - about a third of the stuff that crops up is stuff that people genuinely used to believe in Britain.