Likely affects every 6+ so they are trying to get by without a recall unless there's some user handling that's the cause. Luckily in Apple store my swap was under warranty and they tried to run tests, but didn't seem successful so they are largely trusting customers. First swap took about 30 mins, second took 15 mins. They are clearly aware it could affect some phones, but they didn't come right out and say it. They just acted as if they've heard the problem many times before.