Excuse My Pedantry...
In fantasy literature, arcana typically refers to the magical or mystical in nature.
It’s kind of like saying Bahamut is not a dragon in real world mythology. Real world rules don’t apply 100% of the time.
Yeah, in fantasy literature and games arcana is usually synonymous with magic (non-elemental magic). Which is why the elementalist has an Arcana trait line. So yes, the latin roots make the word redundant in real world context – but in fantasy it has a slightly different meaning (one that is derived from the actual meaning of course, but it nonetheless used differently).
OP your pedantry is utterly forgiven, I thought exactly the same thing
However I did also spend a very happy half hour last night organising my bank slots. Welcome to my world lol