Classic asymmetric design: the recorder gets a persistent on-screen indicator, the person being recorded gets a one-time audio alert they can easily miss. That's not a privacy feature, that's a liability shield dressed up as one.

I guess that Apple can add a feature that listens to all your phone calls to check for the telltale "this call is being recorded..." signal to display a persistent notification. But this article seems to imply this is some kind of special problem for iPhone to iPhone calls, when the issue is for any phone call, a technology that's not unique to iPhones.