Both things could be true.

7-11 theoretically already has it for their app; you scan with your phone and pay with Apple or Google Pay. The only thing is that you’re supposed to sort of wave the completed transaction at the cashier as you go, but the only reason you’d really need to use portable self-checkout is if the cashier is busy, and when they’re busy they don’t want you breaking in line or to stop what they’re doing to see that you’re showing them a plausibly legitimate checkout screen.

In a completely, utterly, definitely unrelated story, I got accused of shoplifting by a 7-11 cashier the other day.