I did something similar, not as extreme. Worked with TT and then color filters, turning them on then off. By the time I finished with settings, I had TT on, color filters off, auto brightness on and the screen looks great. Same for my wife's 11 Pro Max.So, you reached the "perfect white" even white the true tone on?
And th end of your suggestion you keep turned on the true tone?
Hard to believe it works, but it worth a try
I am a retired EE, but also a Nikon Pro that shot a lot of technical research material. I am super sensitive to accurate color and white balance. My phone is pleasant to view now.