It says in the article that the idea behind this implementation is that if the tag is swapped it breaks the authentication since the glue is involved in authenticating. NFC/RFID chips can just be swapped from a real product to a fake one as-is.
>What prevents somebody from scanning it and reconstructing the position of the metal pieces?
You're talking about very, very small pieces of metal whose position/orientation is not deterministic when laying the glue and that information is combined with the tag itself to present some kind of challenge response.
>What prevents somebody from scanning it and reconstructing the position of the metal pieces?
You're talking about very, very small pieces of metal whose position/orientation is not deterministic when laying the glue and that information is combined with the tag itself to present some kind of challenge response.