Entirely AppKit? Do you have a source? I'm skeptical because it seems to behave like an iOS app ported to the Mac and has the exact same interface layout as the iOS app. Beside that, maintaining a separate AppKit implementation would be a lot of extra work that doesn't seem worth it (though of course, if anyone has money to burn on that, it's OpenAI).
I suppose it's more likely that the main chat interface and other highly custom views have separate implementations on macOS and iOS, while the Settings view is shared SwiftUI code (since it's just a lot of buttons and toggles).
