The tag contains the data who the payment is for and how much the payment is. You could do the exact same thing with QR, but with more fussing and aiming and worrying about the amount of light and whether the image is dirty or not.
But with much better UX and Security. QR Code does have its uses, but for many things it is the wrong solution.
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And since the nfc tags will have a predetermined, set payment amount associated with them, even biometrics shouldn’t be necessary.
That only works with active NFC readers though. Presumably these tags are passive and aren't emitting a signal that would wake up the iPhone