Ford's F-150 screen was a much more common width-to-height ratio within Google's parameters, that's why you got full screen Google Maps when you did. RAM's portrait style 14.5"s screen is unique and less common, although I thought I noticed GMC using a similar portrait-style screen layout in their new Yukons, whereas Tahoe's were staying in landscape view.
Autolinkr (and similar devices like CarPC, Ottocast, and Calinkit AI) do not make Android Auto full-screen; they cheat and bypass Google's projection rules entirely. Autolinkr is not an Android Auto device. It's a full Android computer running Android 13/14, the real Google Maps (the phone app, not Android Auto Maps,) and any other Android app you install. It then casts its own screen to the Uconnect display using a custom video protocol. It essentially replaced Android Auto with a full Android tablet running inside your truck.
Google restricts Android Auto to specific aspect ratios, but Google does not restrict Android screen mirroring, Android tablets, or Android apps running on external hardware. Autolinkr uses this loophole. It's not Android Auto, it's not bound by Google’s projection container, it can output any resolution the car accepts, and it can fill the entire 14.5" RAM screen.
When Autolinkr is active, the RAM thinks it is receiving a generic video stream from a generic Android device, at a resolution matching the full 14.5" panel. RAM does not know it’s Google Maps, it just sees “video input.” That’s why the borders disappear.