This post is from the Activity iPhone Duo UIKit Q&A.
Can an iPhone-only app that fully supports iPhone Duo, but is not otherwise optimized for iPad (and is non-universal), opt out of free-form resizing on iPad?
No. As mentioned in the "Modernize your UIKit app" WWDC talk, iPhone apps running in iPhone Mirroring and on iPad will be expected to resize as well:
https://developer.apple.com/videos/play/wwdc2026/278/?time=92
