Not saying this could be the cause of it, but it looks like the left phone has a screen protector on it, where the right one doesn't? Maybe the screen protector has some kind of UV filter or a slightly yellow tint to it so that could cause your screen to look warmer, even with True Tone and Night shift modes off.
I noticed that my phone is similar to the left one and it has the Belkin glass screen protector from Apple on it. I don't necessarily remember my screen being yellow out of the box and after the screen protector was installed at the Apple Store, it looks a littler more yellow.
I don't really want to remove my overly priced screen protector but I'm curious if that would be the cause of a lot of these "yellow" screens.
Of course, we could just be more used to the "blue" LCD screens that have been on the iPhones since the beginning of time, but the X is also Dolby Vision calibrated so that could also have something to do with the supposedly more natural tones.
My night shift is off....
Its changing to blue and yellow tint...
I compared it to one display here in my office...
My display is very yellowish now....