Also, non-genuine display modules can utterly suck. The most obvious failure is linearly polarized light output. Bonus points for horizontally or vertically polarized light — diagonal is at least somewhat tolerable.
That's not a failure of the display module per se, but a dealer handwaving "suitable substitute" without authority while failing to satisfy a performance requirement that's observable but not abundantly obvious.
In other words, third parties without privileged design knowledge tend to operate on a naive "it's a suitable substitute because it fits" paradigm, which is good enough in many cases, but the risk of a repair based on this model being met with dissatisfaction tends to increase with the character/complexity of a replaceable component and/or sub-assembly, which may not be independently discoverable or even documented.
As a trivial example, you may independently observe a simple 470-ohm 0805 SMT resistor in my design, and you could certainly purchase a quality replacement on the market that "fits"...but the unacknowledged risk in doing so is not knowing with certainty whether my design intent surrounding that component depends on other salient characteristics, e.g. composition, power rating, tempco, operating range, endurance, etc.
If you wear polarized lenses, like good sunglasses out in the sun, polarization angle changes visibility of your screen.
It can make your screen completely illegible if not created with forethought.
The IPS iPhone SE 2000 has a fancy polarizer that is never fully opaque in any orientation. I've seen this on other phones too. I believe it's pixel-level polarization.
Some of the screens might be different on each subpixel, making the screen not-blue for example when you're wearing polarized sunglasses.
I’ve never found credible information online, but I haven’t looked that hard.
This is infinitely better than a black screen, which is what you get with linearly polarized screens.