This is, as far as I know, quite a frequently asked question or misconception… I’ve written so extensively on it yet that there’s probably not much to add at this moment.
I could, perhaps, sum up another thing and make a long story short: if there’s 50 or more (for higher rarities) coins in any of the 5 items from the packs, then that’s the one with duplicate protection, others can — oh, I am repeating myself after all — contain anything. If, however, all items with coins contain fewer than that (the range is specified in the support article), then there might be a problem.
Actually, that one should count for the puspose of duplicate protection.
Otherwise, though, I concur with your conclusion.
It has been considered ‘owned’ from the very beginning (or nearly), as far as I know. See also above about duplicate protection (although I’m not prepared to trace the original source of that information at the moment, but we’ll consider Old Guardian’s reference of it reliable for now).