My '12 works the same way. If it's not dark enough to trip the dash sensor, then the dash gauge backlights do not come on with the headlights. I have the auto headlight position in my headlight switch, but I don't use it. I can manually turn my headlights on and off just fine.

Just to be clear, in my truck it doesn't matter if you use the manual switch position or the auto position, the gauge lights don't come on unless it is dark inside the truck.

I guess I'm just used to it.