This is a pretty awful change, as Apple hasn't defined what “large” means.
So our existing popover view controllers with translucent background suddenly start showing an opaque background when they exceed some arbitrary size? I noticed this on a popover alert which shows a transparent background running in English, but an opaque background running in German, because the latter is slightly more verbose and takes up a slightly larger amount of screen. An App should never change the presentation style just because the user's selected language is different.
Our specific scenario is presenting alerts as popovers above an Augmented Reality view. It is important to us that the user doesn't lose sight of their AR environment, which is why we want to preserve the transparent background of the popover.
Apple has a great track record for preserving backward compatibility, but this time it's broken. Even if this is the new "default" behaviour, it would really help if we could disable it programmatically for scenarios where we really do not want the OS to make such an arbitrary change in presentation.
Please consider amending the API so we can either disable or "tune" this new presentation style to preserve our existing UI appearance.