Just curious, what is the brightness level of the iPhone display, and how does the HDR histogram change if you change the brightness? Normally, as you raise the brightness, the white bars get shorter under the HDR histogram (because there’s less headroom for previewing HDR highlights), but on my iPhone it still shows about half a white bar at full brightness.
If the HDR histogram does not change or show white bars even if you reduce brightness all the way, then that is definitely not normal and something is wrong somewhere.
Also, I just thought of something else, when I was trying to think of ways the iPhone display might be altered: In iOS Settings, do you have any visual Accessibility options enabled? I did an experiment on my iPhone: In the Accessibility settings, I enabled the Reduce White Point option, and bam…HDR range goes all red. Which makes sense, because that setting further limits display of highlights. I sometimes like to use Reduce White Point when even the minimum brightness is too bright at night, so I assigned it an Accessibility Shortcut, which I sometimes activate by mistake during the day…and when that happens, the display isn’t as bright as it should be. If this is not the answer, I hope that it at least points you in the right direction.
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