You don’t have to necessarily use the phone to use the fastpass and give them information. Your account is linked to the app in your cellphone and when you walk up and scan your band, that information is linked to the app. They could see how long your wait in the fp line is without using your band and just using the your cellphone if it is on you with the app running. MDE has your location on it for the maps in the park.So how would that work at the FastPass entry? I have to take out my phone, unlock it, select who is using the FastPass, then tap it? Also ripe for abuse. The cast member will have to look at a screen to see how many FastPasses I'm using with my phone and if it matches the # of people in my party. That seems a lot more friction than simply tapping a magic band for each person and having the light turn green....
BUT if they went strictly to no magic bands nd it’s cell phones I’m sure they could come up with a barcode that scans for each individual person in your party