Colour profiles, dead pixels etc are a part of the DNG specification. Sensor tiles I don't think so. Diffraction is aperture only. Lens correction parameters are also part of the DNG spec.
If you implement reading of DNG correctly, you can process any image from any camera that has been converted to DNG. It is just another raw format, except being well defined.
Anyway, the discussion is not about Capture One supporting DNG or not but about blocking certain cameras based camera names. Just changing spelling solves that problem. It may be that inferior conversion may result using DNG, but I wouldn't think that is the case.
If a Phase One customer has extensively used Capture One and plans to use a non Team Phase One MFD he needs to ditch his experience with Capture One and his frustration is understandable.
Just to check out, I took one of the few ARW images I have from my A7rII, exported to DNG. Opened both images in Capture one, made some edits, copied the adjustments, exported both images and opened them on top of each other in Photoshop. No real difference when flipping layers on.
Than I made the ultimate test, subtracting the layers. The image came up black! It was not as simple that C1 was using just the pixel data, as I tried to copy the white balance from the ARW image to the DNG image and that failed miserably. That means Capture One processess an A7rII image near identically weather shown it as ARW or DNG.
The first enclosed image shows the two images layered, with a mask applied so part is ARW and part is DNG. The second one is the difference image. The histogram shows they are not identical.
Sure, and a basic conversion will be the result, but that's not a highly optimized conversion (profiles, colors, mapping of dead pixels, calibration of e.g. sensor tiles, noise reduction settings for different ISOs, etc., and whatever other secret sauce is hidden in the EXIF maker notes). Lens parameters will also need to be separately defined because Adobe uses its own models for that, and that might also affect things like diffraction correction and other/future features. That would require shooting hundreds of images and tweaking of many settings, so it does take a lot of additional work.
It would also require a significant number of potential licensees to make the investment of resources worth while, and the GFX might create a tipping point, who knows.
Not that the basic conversion is that bad, but when pushing things to the limit the additional refinements will pay off.