Android games are added automatically on startup, if it's enabled in the options. They show up under the Android platform. But unfortunately, Android does not provide a good way (outside of unavailable information from the Play Store) to determine what apps are games and what apps aren't. So unfortunately, there's no better way to auto-import all installed Android games.
That said, yes, I can see how an opt-in option would be a good one. However, you can basically get there already just be deleting any non-game apps from the platform. They should not show back up.