If Adobe products already read the Phase One TIFFs and will change them into DNG why would PO even bother to output their flavor of DNG that essentially doesn't provide any advantage?
advantage of DNG is, that it offers a common platform for adjusted raw data
. This means, that a certain raw processor/preprocessor does not need to carry out all the functions the usual raw converters do but "add their knowledge" and let the DNG-aware raw processor do the rest.
Example: certain MFDBs create a "camera profile" describing certain characteristics of a specific camera copy
. This profile needs to be involved in the raw conversion, but this is not covered by DNG. The raw (pre)processor can apply the "knowledge" from this specific source and create a DNG file, which is not "really raw" but "raw enough" to be processed by any DNG aware raw converter.
There is no written rule how far the DNG preprocessor can go, but the farther it goes, the less freedom the next stage has.
For example the "small raw" creature of some cameras creates a "raw" file, which is de-mosaiced. This step offers certain advantages, but it removes the option of choosing from different demosaicing algorythms, as some raw converters offer.