I am not going to enter the debate between Ostia and Bartel because you are both kind of right and kind of wrong.
Ostia is right about materia being built off the idea that espers laid out before. But in that same explanation was proof that VII did not copy materia from Ultima. FFVI predates Ultima Online.
All games borrow from others whether we like it or not. I'd much rather have ARR borrow from it's own franchise than other franchises. That by nature makes it not spontaneous original but original nonetheless since the same company came up with origin.
I wish Matsui would ask Ito to help design some mechanics to add to the game in some areas. The man is a genius.