Hello
This is not a new behavior in Lightroom, or iOS, or even this year's new phones. Lightroom QA logged this behavior as a bug several times, and each time the feedback from developers was that the Lightroom is simply writing the raw image data directly as the sensor provides it. Lightroom DNGs look different from capture review mode in the screenshot above or when compared to JPGs due to processing iOS does for the JPGs its APIs render for Lightroom (that review mode image is actually a JPG that gets rendered and displayed in capture review and is not the actual raw DNG image captured).
When capturing in Lightroom's DNG format, one can use exposure compensation to increase or decrease exposure. I personally prefer to let DNGs capture at autoexposure, and then modify the exposure when needed in Edit more. Auto usually gets me closer to desired appearance. I prefer this overall to JPG capture, which simply lacks the greater image data DNGs have that allow more flexibility when editing.
The LR engineering team will continue to explore options for future releases.