Neither DNG nor various vendor-specific raw formats are meant for tuning an image sensor. They can be used for that in some specific cases, but it's not what they are for. They're for taking photos and providing the user with less opinionated data so they can do the processing of their photos the way they want rather than rely on predefined processing pipeline implemented in the camera.

Despite the name, this is rarely a pure raw stream of data coming from the sensor. It's usually close enough for practical photographic purposes though.

Our proprietary format was a header followed by a raw sensor dump.

Despite this, people eventually used it for photographic purposes.

So is DNG in the implementation I've worked on (data as outputted by the sensor wrapped in a TIFF structure), but whether what the sensor outputs is actually "raw" can be debatable and is sensor- and configuration-dependent.

Absolutely true. Our sensors would dump their registers in the first few lines so at least you knew what settings were used for that frame.