An iPhone 13 mini can only just barely read the QR Pass (printed at 100% scale resulting in it being at 2.6 cm sq) but my Zebra DS2208 handheld scanner reads it quite easily.
The error in my mind is that the government's smartphone app needs to work robustly on any smartphone. I think the code would need to fill up the width of the "business card" size to order to achieve that.