PSBTs off QR codes is a hack, look no further than the rolling QR Codes for multi-sig. if you really dig into it with a tinfoil hat, passing PSBTs off SD cards is actually safer -- less dependencies at the end of the day, no different than USB? what interface do you think your camera runs off of?

another innovation you don't see elsewhere? NFC that you can turn off physically

I don't even have a cold card 🤣 I give props because it is deserved.