Is it essential to include an app exit/close/quit app button in the app?

In Carmack's review of this app he says it isn't necessary:

https://developer.oculus.com/blog/carmacks-app-reviews-space-shooter/

"Having an explicit “exit” option in the UI is discouraged. Users are expected to use the universal system level functionality to exit apps instead of learning a per-app option, and “exit” can be incorrectly interpreted as “exit to menu” instead of “exit game.""