Well, I don’t know. I’ve been using UniWB even for interpolating raw files for a long time now, not always, but for specific images, for various reasons, and then setting the white balance in my patched version of high bit depth GIMP (“GIMP-CCE”).
I do this by outputting as raw color from dcraw and applying a custom camera profile from disk, which profile is also a well-behaved RGB matrix working space profile, made using this procedure: https://ninedegreesbelow.com/photography/well-behaved-camera-profile.html
Or else I use PhotoFlow and use my camera input profile as the output profile. Or etc. I’ve never noticed any problems applying the white balance in GIMP-CCE instead of before interpolating the raw file. But you all have made me very curious about artifacts that might or might not result from whatever white balance is set before interpolation.
I have to say that as a confirmed pixel peeper I’ve never noticed any problems using UniWB as the white balance for interpolating raw files. But on the other hand, I’ve never been very happy with the whole process of white balancing raw files, whether before or after interpolation and regardless of the white balance used during interpolation - but to be completely honest here, I’m not even sure what it is about the process that makes me uneasy . . .
So I’m doing some experimenting and will share results when I’m done. This might take a day or two. Hopefully other people might also experiment and share results.