I don't think it's necessary if the muscles and muscle memory is built up from live fire.
But if the trigger press isn't fully developed and the different types of trigger presses for different target difficulty isn't fully developed... this can be a good workout and a way to burn in proper fundamentals rather than imagining it.
These days I am using a DASA gun for dry fire and I don't have a resetting trigger per se for my SA shots and it doesn't really matter.
But I think since guys like Max take the time to reset for their first shot, they'd use a reset trigger system if it were available for P320s... if it were faithful enough. But since Max and Lenny Magill are partnering on other things maybe Lenny could make a P320 resetting trigger kit too. Might be harder since it's integrated into an FCU for that unit.