do you actually gain access to the wallet from nfc or is it just watching only?
In both cases this has big downsides. In the first case you need to check every note that there is still btc on it. And the previous owner may still hack it and potentially spend afterwards. In the second case you need to trust the issuer that they will actually pay you the btc on demand. And you never know if your watching wallet is also used for another note.
Yeah! I agree that the technical limitations, bugs or possible exploits in this are crazy.