Part of owning a truck is having confidence in it. I would take it into the dealer and explain what you are feeling/seeing. They will check it out.
Even if you previously had a gasser, there is a bit of a learning curve. But, that should only be regarding the auto-downshift in Tow-Haul mode and use of the Manual Shift. Seeing the Rev Limiter cut in at 3200 throws you the first couple times too. But other than that, my '09 DMax feels like it is operating just like my gassers. I have never felt like it was free-wheeling. Even at 45 or below you can still feel the engine drag, especially when it was new.
On a side note:
When you get a new vehicle and think there is anything wrong, get it in to the dealer and record the problem. Who knows, you may end up lemoning the truck and you want any lemon qualifying incident recorded as soon as possible. In Mich we only pay 10 cents per mile to the first lemon qualifying incident.
I lemoned my 96 Chev gasser. Luckily, I recorded the passenger door not opening at 640 miles. After the truck fuel injectors went bad twice, had a fire in the dash and several other significant problems, I lemoned it on the passenger door not opening. Three times, I took it in for the door and still ended up fixing it myself by taking out the door rod, re-bending it and tempering the bend. In Mich, when you loose confidence in the vehicle, the vehicle qualifies as a lemon. Three failures on any same sub-system, is adequate reason, according to the Mich law, to loose confidence the vehicle.
It took them a full year to get through court. On the last day GM settled, which is GM's strategy. They hope you quit paying on the loan or wreck the vehicle, before they have to settle. Somehow, I still made over $500 on the deal, even though I drove it 79K miles, got all my payments & interest back and had a lawyer involved.
Lots of headaches with the truck though. But, when you have to have repairs made and you are in the lemon process, always press for a loaner. Once they know you are lemoning, you will get one.
But, we are nowhere near lemoning here. My point is once you loose confidence in it, the truck is a lemon, in Mich. Even the simplest of things that goes wrong could come into play. So register even the little things with the dealer ASAP. Failure to so may cost you in the long run.