Under steady state with constant mass flow rate of the dry air component, the volumetric flow rate of a humid air mixture MAY change between a State1 and State2. Some special processes may follow a specific volume per dry air isoline (sometimes shown Psychrometrics charts), but in general it may vary.
This is sometimes "glossed over" in some online calculators and less formal guides. More specifically, it is not always stated whether a given volumetric "air flow rate" refers to the entry air flow rate at initial State1: