From the 2013 Ram owner's manual:
This electronically shifted transfer case is designed to be
driven in the two–wheel drive position (2WD) or fourwheel
drive position (4WD AUTO) for normal street and
highway conditions on dry hard surfaced roads). Driving
the vehicle in 2WD will have greater fuel economy
benefits as the front axle is not engaged in 2WD.
For variable driving conditions, the 4WD AUTO mode
can be used. In this mode, the front axle is engaged, but
the vehicle’s power is sent to the rear wheels. Four-wheel
drive will be automatically engaged when the vehicle
senses a loss of traction. Because the front axle is engaged,
this mode will result in lower fuel economy than
the 2WD mode.
When additional traction is required, the transfer case
4WD LOCK and 4WD LOW positions can be used to lock
the front and rear driveshafts together forcing the front
and rear wheels to rotate at the same speed. This is
accomplished by rotating the 4WD Control Switch to the
desired position. Refer to “Shifting Procedure” for specific
shifting instructions. The 4WD LOCK and 4WD
LOW positions are designed for loose, slippery road
surfaces only. Driving in the 4WD LOCK and 4WD LOW
positions on dry hard surfaced roads may cause increased
tire wear and damage to the driveline components
The question isn't if the full time xfer case is working as designed, rather than is it working as Ram marketed it. I'd show the dealer the manual and tell them to make it work this way.
Also keep records of your visits/complaints for this problem as you may end up with recourse through your local lemon law if they can't make it happen.
The owner's manual clearly doesn't differentiate any difference in operation in 4wd lock between the two available transfer cases.
Edit - I also just checked my 2014 owner's manual and it says the same thing.