Honestly, doesn't seem all that hard to slip through to me. For manual testing, QA sets up and shares a bunch of test accounts - they wouldn't remember that a device is only supposed to see Test1, Test2, and Test4 but not Test3.
For the automated test, just verify that the expected accounts show up and forget to also verify that the unexpected accounts don't show up.
This is why you don't go straight from QA testing to production though... should have a dog food step inbetween where all your employees can beta test before it goes to a wide release.