The Xperia 1 features a 4K OLED display and, unlike the XZ Premium and XZ2 Premium that only rendered in 4K while viewing content of that resolution, the Xperia 1 will be a full-time 4K display. Yes, even when in system apps like Gallery and Settings.
https://www.notebookcheck.net/The-Sony-Xperia-1-s-display-has-a-full-time-4K-resolution.414947.0.html
Two mistakes, Sony is still the only one with 4K screens on mobile. Their first 4k mobile was not the XZ premium, but the Z5 Premium in 2015.
I owned the xz premium, had it altered for 4K full time, it doesn't just look nice,,,, IT'S FREAKING FAR OUT, INCREDIBLE, MAGNIFICO, ESTUPENDO,.. MAN !
Not getting it because of the screen ratio is ugly. I like my XZ2 premiums 16:9. I have it modified via ADB settings to output 4k all the time but screenshots and vr is out of margins after Android update. It is still amazing for normal use though and zero battery life impact I noticed.