They are manufactured under licence by a different company here in Canada. I actually have one in my home. I purchased it and am gutting it, planned to replace the panel, but have later discovered that the manufacturer in Canada passed third party testing of their product. I did have some issues with the way things were wired for my dryer (new dryer pulling too much for the breaker). Tripped once and I re-set it. Tripped again, I called an electrician. While he was there we tripped it multiple times as he was curious too. I've even tested some receptacle circuits and they have always tripped.
Since the failure rate on the breakers was something like 50%, either I am very lucky and have managed to get good breakers, or the ones manufactured in Canada do not suffer from the same problems that their US counterparts do.