There can definitely be variances in the iphone x displays, which frankly surprises me. From the tech side, certainly it can happen but I would have thought that apple would REALLY have had some extreme QA on the iphone x for at least the first batches. But, maybe they were just so short the displays (or cameras or something) that every display that wasn't clearly deficient made it into a phone.
My iphone x from launch day was clearly more yellow and muted than another one on display in the store. Same settings, same true tone, on or off, same brightness, side by side it was very clear.
In the end, I returned it. Might go with an 8+ instead but at a minimum I didn't really want that display all the time. It didn't make consuming even text content very satisfying. Also, for such a premium $$ phone, really it should be unquestionable from a quality standpoint.