There is definitely a lot more backend real-time checking of names and FFP account status happening within Star Alliance than used to be the case, and this comes with some problems with getting mileage credit. For example, I was trying to add an A3 frequent flyer number into a UA booking and it wouldn’t take even at check-in. The A3 account number hadn’t been used since probably a 2013 safari trip, so it was probably a shut down account. A new A3 account was opened, and the fresh A3 number got accepted into the booking without issue. [Well, except A3 later wanted to be emailed a bunch of stuff to verify the person’s existence being consistent with the names, date of birth and address on file…. but that’s a story to itself.]. Keep in mind that flying on UA flights requires showing ID to get airside or board UA flights.]