Ever since the iPhone X, upside-down orientation on the iPhone has been disabled by design. I haven't found any official documentation explaining why, but my guess is it has to do with Face ID and the top notch.
However, now that the iPhone Duo has no Face ID or notch—and includes reserved occlusion regions—why not enable upside-down rotation?
As of iOS 27.1, it remains disabled. Leaving it turned off only confuses users, making them think their favorite apps are frozen when they won't rotate.
