It’s never really needed to to be honest. No matter how dark or bright sunlight there is I’ve never gone above 50% manually, the phone adjusts higher in bright sunlight. IPS LCD has fared very very well over the years and had better colour accuracy and readability in direct sunlight compared to the over contrast and high tint like nature is Samsung’s AMOLED that pretty much all androids changed to years ago.
Now Apple uses OLED much more improved (I resisted it for a while to be honest) screen that has advantages of both.
Curious when have you ever needed an iPhone screen to be brighter than it can go? (Besides flashlights).
Good question, as mentioned presently you do not exceed your AMOLED/LCD brightness past 50% (presently at 650 nits). Let say that AMOLED/LCD brightness is doubled (1300 nits), that would mean that to get the same amount of brightness presently at 50% with doubling the nits you will get it at 25% if not less. When any display brightness raises above 0% it takes more battery power. The brighter the display the less power it takes at low settings.
This is used for example purposes:
Present AMOLED brightness 650 nits:
10% brightness battery life usage 12 hrs.
25% brightness ... 11.5 hrs.
50% brightness ... 11 hrs.
75% brightness ...10.5 hrs.
100% brightness ... 10 hrs.
Now lets factors in other activities, gaming, listening to music, BT, LTE, WiFi, browsing, recording video, etc. That will further reduce battery usage time. IOS does a great job juggling battery efficiency, however making minor improvement here and there will only increase usage time, for example dark mode on iOS.
Once again this is only used as an example.
If you are using the screen in sunlight conditions, at higher nits the screen does not have to jump from 10% to 25% brightness. It can make an incremental change from 10% to 15% to achieve the desirable effect, thus using less battery power. At the end of the day have a larger battery is great, however having efficient use of that battery is even better.
I am in the crowd that uses their device on 5% brightness and only rarely increase it to 25% due to ambient lighting conditions. With the increase in nits I can have the display set at 1% and increase it to 10% on rare occasions, thus increasing battery efficiency.