Is this issue you are discussing the reason for the current "bug" with LCC correction and green shift, and what 9.0.3 is supposed to resolve? Is it bad enough you feel software changes won't "fix" it, or at least won't fix it some of the time?
It's a problem that's very hard to fix in software. I've myself tried to make a crosstalk cancellation algorithm when the IQ250 was new and this problem became more evident than ever, so that's why it's a "pet issue" for me.
What I did back than was to try to mathematically solve the issue, that is shift the crosstalk backwards. The problem is that you need to start from an area without crosstalk (ie center of the lens) and then calculate backwards from there, and when you chain several thousands of pixels like that the small errors and it becomes impossible to get a stable algorithm.
To "fix" it in software you instead need to hide it. It's easy to look into the LCC shot and see where green1 and green2 separates, and then equalize greens in those areas (at the cost of detail), then mazing will never occur. I do that already in my own LCC algorithm, but I don't think Capture One does it
yet as I've seen reports of mazing still. If you do that you only have the color and tonality issues left, that is as channels are mixed up saturation and color separation goes down and there can be some hue shift.
It's a matter of taste how large issue you think this is. If you want to you can see it as a form of vignetting, "tonality vignetting" (it's not the same circular shape though!), and even think of it as a subtle creative effect. Or you can see it like this -- "why am I spending $44k on a back which is not designed for these lenses, and even think about compromising tonality?".
I think both conclusions are valid, I just want people to know what they are doing. I do find it surprising that many tech wide users are so obsessed by sharpness, and don't seem to worry much at all about tonality. What would you rather have, perfect color/tonality or perfect sharpness? We make hugely technical analysis of sharpness and DR, and I think this issue also deserves attention. It does get it but I think the issue of subject-dependency is a bit lacking. By explaining it in more detail in this thread I hope other technical-minded analysts that actually have access to this back (I don't) can make their own more detailed investigations.
Standard color cast is a calculated issue which can be fully neutralized with the simplest of LCC algorithms, it's as simple as neutralizing vignetting. This was an intentional tradeoff to allow for symmetrical and weak retrofocus lenses which is the
foundation of the unique tech wide angle performance. Rodenstock designers did not have the intention to push the sensors into large amounts of crosstalk though, but they couldn't foresee what sensors would appear in the future. If they had known about where sensors would go the wide angles would not have been designed the way they are today. There is a critical issue here though, the more the tech wides are forced into retrofocus the harder it becomes to retain their unique performance. At some point it becomes unfeasible.