https://www.theverge.com/circuitbreaker/2018/10/19/18001278/google-pixel-3-screen-corners-rounder-software-display-change

Google is extending its design atheistic that favors subtle, rounded corners even further by manually adjusting the Pixel 3’s screen corners during start up, as first spotted by an eagle-eyed Reddit user earlier today. Material Theme, an updated version of the company’s software design philosophy, is the driving force behind the Gmail and Chrome redesigns of late, and you’ll notice it most prevalently in the new Chrome tab design that eschews rough and pronounced corners for softer, rounded ones.

Google isn’t going so far as to turn the edges of the Pixel 3 display into Chrome tab replicas, but it is using a subtle software trick to “shrink” the radius of each corner of the display to produce more rounded corners. The radii change means that the Pixel 3 screen isn’t using the available screen real estate at its absolute maximum, though it’s a pretty much imperceptible cutoff unless you closely observe the change during the phone’s start up phase.