Looks like my terminology is backwards.
From NEMA AB-3 2001 (para 3.1.5) a multi-pole breaker normally has an internal common trip and a two-pole breaker may have an independent trip.
The UL White book DIVQ says that independent trip units may be used on MWBC that include a grounded neutral even if there are L-L loads. But it goes on to say that multi-pole common trip devices may be used with L-L circuits that do not have a neutral.
