To be fair, I think his educated guess has a high degree of confidence (from my own educated guesswork).
It relies on it being what they did. He cannot know that, only guess it. Yet it is presented as fact, not guess.
When I said "it might re-beige all the planets" it was not stated as a fact it would, that it could. A claim based on being ignorant of what they DID do, since there's no way to get from not knowing what they did to what changing it would do. We still don't know why the planets beiged.
They may not have any reason not to do it except they can't be bothered.
They may not do it because making it player controlled could be exploited or present a massive new UI for multidimensional colour grading in the game, or because it has OTHER changes BEFORE the postprocessing that the postprocessing is then making good on.
Like full screen motion blur. Without it, a game might be relying on the blur to allow cheaper (fewer) interpolations to get movement animation, so taking away motion blur will show up that the animation is a bit "Harryhausen", so more animation keypoints are needed, increasing the load of the graphical engine and degrading the "player experience".
The colour grading is likely a full screen artifact and, given the claims it does not impact performance at all, almost definitely a single end pass postprocessing.
We don't know what THIS VERSION OF THE ENGINE looks like without it.
If they have a reason for not changing, that would be one I could see as rational.
We'd be guessing without FD's input.
And those professing professional chops on the subject have more need to retain such qualifiers to their claims lest it fall foul of the argument by authority fallacy.