While I mostly agree with you, this is the kind of thing that might not have been done if the AI couldn't do the heavy lifting.

They had previously chosen React Native because it was easier for programmers to keep it updated, since it was really just 1 codebase. With AI, those same programmers can do the more difficult version, keeping the native apps updated separately.

So did it kill a job, or did it make it possible for the existing programmers to do it better?

It's the kind of thing that is really hard to determine in general, but here, it really does sound like they only made the change because it became possible with existing resources. They would not have done it otherwise.