Mario Kart 8 DX, ARMS, NES Online, and Mario Tennis Aces all support the app for voice chat. Splatoon 2 is the only game that has an extra service at the moment.
That's a little better. Wish I'd known! I'd love to have talked smack in MK8. I'm curious what's the difference between Splatoon and the other games, now. Game invites?