Adding my voice to the noise. Apple fanboy here. I got an iPhone 12 Pro on Day 1 and went to post a photo I had edited on Lightroom on the Mac to IG and noticed it was WAY warmer on my phone. Went crazy and did side-by-side comparisons of older iPhones I have here, my iPad Pro, other Macs, and sure enough, the 12 Pro had a yellow-green color cast.
I made a Genius Bar appointment and compared my screen to the store models. The tint issue was present on all the 12 and 12 Pro models but not on any of the older phones. The genius didn't see what I was seeing and asserted I was being too picky. ...I returned the phone and have been using my X since.
Would love to upgrade to a 12 again but I can't as long as the screen issue persists. I'm a photographer and color is everything. Why spend all the time fussing with white balance and colors if they end up getting viewed on a phone that makes all that effort worth nothing? I'm assuming this is a known issue. It's the only screen in the Apple ecosystem, for at least the last 12 years I've been in it, that hasn't matched all the others.