> I realize they have a lot of different models and probably a limited test matrix

Why would that be hard? They're the manufacturer; all they have to do is keep a handful of every model they've made, stick them in a room connected to network and power, and have Jenkins run a job on them that flashes the firmware and reboots. I know I'm oversimplifying, but I don't think I'm oversimplifying by that much, and it shouldn't be hard for the manufacturer to keep test units of their own hardware on hand.