This is patently false. If you turn off your WiFi, 4G, Bluetooth and NFC, and only use your phone for calls and SMS, a smartphone can easily last a week. More than a dumbphone with the same features.
Agreed. You can also lower the brightness of the screen when you don't need it. My Sony Xperia Z5 Compact in "Stamina Mode" (basically what you're describing) can last for 7-8 days as far as I can tell.
That's a problem for trucks and buses though.
They have a different Problem and might need a different solution. Hydrogen might be cost effective at truck-scale.
I'm convinced that ammonia will be used rather than hydrogen for these applications, but it amounts to the same thing.
Compressed natural gas is used in some buses right now.