If you ever got involved in the SqD/C-H debacle you will see US manufacturers go out of their way to say you can only use their breakers in their panels on their labels. NEC 110.3(B) is used as the justification.
Personally I see this as pure marketing hype, with the same validation as the statement on a Lays potato chip bag that says these go best with a Pepsi but that is just one man's opinion.
The fact remains there are plenty of breakers that "fit" in other panels but that does not mean they are classified for them or even that an inspector has to honor classification if the label prohibits them.
This is a very muddy area.
