[tasqa]

As other said it is not necessarily about the using the phone it's about the light emitted from screens of all our devices. T he issue also applies to using other screens at night. Like watching TV right until you go to bed, or even in bed. I guess using your phone in bed to set an alarm and whatnot is a more common case and thus is used as the example.

[dexterdog]

Do people not put their phones face-down in the night table?

[Anechoic]

I used to, but as of iOS 9, "hey Siri" no longer works when an iPhone is face down so now it stays face up at night.