But in the early days, a lot of UI and OS frameworks were based on Carbon stuff ported from Classic MacOS with Cocoa wrappers on them.

One sibling mentioned the menus. Another sibling mentioned the Security framework. The SDK for macOS Golden Gate still ships with headers dating back to MacOS 8.6 (although they are mostly deprecated now) https://kalleboo.com/linked/macos86security_vs_macosgoldenga...