Which Raw Format?

Precisely!

And Adobe products, and as far as I can tell many others, can render a DNG image without using the data in DNGPrivateData, which the specified way for storing such data.

The Adobe DNG Converter stores the original Exif MakerNote in DNGPrivateData. So any software that understands the Exif Makernote can extract and use it from the DNG file. The Adobe DNG Converter typically also extracts certain fields from the Makernote and determines the values of some of the standard DNG fields from them. So those fields become more "open" and there is no need for DNG-readers to look in the Makernote for them.

The way the Makernote is stored in DNGPrivateData is here.