"Discovered, not invented" is the 3e designers' way of saying "please don't think too hard about this: we're not going to explain it any more, and we really hope the debates that plagued AD&D will go away and not bother 3e."
Lots of design details in 3.x like this, that might not make sense at first, are simply attempts to handwave having to explain how something that has to work a certain way mechanically actually works fictionally. AD&D was full of such details, and players and DMs debated minute details of how spell components and wishes actually worked to the point where there were thousands of column-inches devoted to "solving" these holes, never to be successful. 3e attempted to break with that tradition by removing such lacunæ from the rules-fiction interface, by using fiat declarations like this. They are, in essence, signs that read "Nothing to see here, please move along."
Given that text like this is deliberately intended to avoid giving an official answer, you will have to be satisfied with ignoring it, or making up your own answers for your own group.