Although the Roman Church moved St. Catherine’s feast day all around the calendar with bewildering frequency, its most popular date was Lammas. (They also kept trying to expel this much-loved saint from the ranks of the blessed because she was mythical rather than historical, and because her worship gave rise to the heretical sect known as the Cathari.)
I don't know about moving her feast day; I do know that I've read that St. Catherine herself was historical, though the details of her biography are as fanciful as many another early saint. Certainly, I know of no attempt in medieval times to restrict interest in her, or to "expel" her from "the ranks of the blessed."
Be that as it may, though, the whole of this writer's credibility is just blown out the window with that mind-boggling reference to the Cathari. The Cathari were not named for St. Catherine. The term goes back to the early Church, and is derived from Greek katharoi, "the pure ones." It was a sarcastic reference to those who thought themselves holier than ordinary Christians, as we would talk today about "Puritans."
Really, the make-it-up-as-you-go-along "scholarship" of the new pagans is embarrassing. I know more about real paganism than they do! As an admirer of all things ancient and Northern, I've read some of the neo-pagan sites; like Tolkien and Lewis, I appreciate the elegiac spirit of the old North and the theory of courage, not to mention the culture and languages. But the attempt to make a modern religion out of the ancient cults simply produces a pastiche of the real thing. For that matter, all the updated paganisms I've seen are heavily indebted to Christianity for their forms and attitudes.
One might regret, along with the Emperor Julian, that the "pale Galilean" has conquered the ancient cults, but they are dead past reviving. Christianity's only real competitors these days are radical Islam and post-modern secularism.