The damage dealt by Volley Veteran is optional. It should therefore read:
The distinction matters in paper MTG (A Flametongue Kavu entering a battlefield with no other creatures in it must kill itself), and so it should matter in MTGPQ too.
Any targeted effect opens a dialog box, allowing you to bypass the effect.
As someone who regularly cites paper versions of cards, I am sympathetic, but this is working as intended.