From Wikipedia: "In thermodynamic systems where the temperature and volume are held constant, the measure of useful work attainable is the Helmholtz free energy function" https://en.wikipedia.org/wiki/Work_(thermodynamics)#Free_energy_and_exergy
By definition, constant volume means that no PV work (expansion work) is done by the system. Because of this, is it not confusing to define Helmholtz free energy as a measure of the maximum useful/non-expansion work attainable at constant volume and temperature rather than just the maximum work attainable at constant volume and temperature, since all work done at constant volume is inherently useful/non-PV work? Adding the "useful" makes it seem like the useful work is separate from work done in general for a constant volume process. Am I missing something?