The rounded corners look ridiculous on this phone. They also cut off a non-trivial part of the displayed content now.
I also like to spectate games on Twitch/Youtube, and corners are often used for important stats.
You can look at other examples of controls that are way too close to the edge because they need to work around the bloated corners.
Of course, some of it is just the usual Apple stupidity and ineptness in the UI design (that infected the whole industry): https://www.apple.com/v/iphone-duo/a/images/overview/shared-...
But rounded corners certainly did not help.
And I'll admit that there's chance I'd notice what you're talking about if I saw/used it in person instead of relying on promotional photos.