Would seem to make sense but they're not reconciling the completion of the FP+ he's in line for before he completes the transaction he's using to lock his acount in
MDE. The time lag shows a probable time initiated batch for ride completion for multiple riders. So, they're not reconciling each individual guest's account or account status at the first or last FP+ scan. Why? - because they can pre-load the data for scheduled riders much earlier since it's a reservation. They can load that the night before, if they want to. And (they thought) just efficiently move any changes, like cancellations.
So, at this stage in the process, they're defaulting to whatever data that's in the user account as true for whatever conflict arises. Meaning, they're discarding the ride complete in favor of the newly stored FP+ reservation.