What are you talking about? I’m talking about Cocoa NSTextField, NSTextView etc., got nothing to with libreadline or bash, unless there’s a history lesson here you’d like to share.
Edit: Your comment was expanded as I was replying / after I replied. From which it’s quite clear you didn’t get my point.
Oh I get it, I think you're just underestimating how much effort Apple's developers put into system-wide consistent behaviors in macOS. And also how picky developers are about keyboard first and changing keybindings.
They decided to use emacs bindings because emacs bindings are the system default for macOS programmers.
Apple's developers were also macOS's first users and they started with a terminal long before they had a working UI.
Reread your comment. I misunderstood the first time round. You presented a theory that Apple implemented Emacs keybindings for Cocoa text input widgets not because of Emacs per se, but rather, mainly for consistency with bash. It's an interesting theory, but without a history lesson backed up by sources it's still a theory.
For the record I don't underestimate how much effort Apple puts into system-wide consistent behaviors in macOS. <s>Also, zsh's default keybinding mode is Emacs mode.</s> (Of course, you did mention that.)
Technically, that was systemwide inconsistent behavior.
Readline compatible keystrokes came from nextstep (sorry, I don’t dare to guess how to capitalize that). Traditional Mac OS used completely different key combinations (command left arrow instead of control-a, for example). Because of that, Carbon apps didn’t support readline-like key combinations (but system input fields did)
The two could happily coexist only because the Mac originally didn’t have control keys (it only got them for supporting terminal programs, as part of trying to make Macs sell better in business), so none of its navigation keystrokes used the control key.
Edit: Your comment was expanded as I was replying / after I replied. From which it’s quite clear you didn’t get my point.