What's with the minimum voltage rating on *some* IEC 60947-2 MCBs?
My interpretation is that there is no minimum voltage and thus not stated but like all contacts >2A there ought to be a minimum current for contact wetting or if non gold alloy plated.

The suitability for low voltage however is usually the over current ratio threshold for a rapid trip.

The Schneider specs of 5x breaker current are similar to the type B MCB’s in this regard as specified suitable for low voltage type PLC’s.

Being thermal-magnetic breakers they have a tighter tolerance for slow over-current from a thermal trigger and a wider over-current spec for more rapid magnetic response.