As purple figment has already pointed out, tickets purchased together are tagged so that the stored finger scans of each member of the party will work with any ticket.
When we visited Epcot in March, we used a new-fangled type of scanner which, I suspect, was in test stage. They were set up in banks of 4 to allow multiple guests to enter at the same time, but it was such a faff that it was just causing chaos. You had to simultaneously laser-scan your ticket's barcode with one hand whilst scanning a finger of the other hand. All available CMs were having to assist every guest and, as there was no turnstile, it would have been easy for hoards of people to just walk past without even having a ticket!