I am still not certain I understand exactly what Apple's reviewer meant by 2.4.5 in my case. My working assumption is that the concern is about an app reaching into every other app on the system to inject text, but I never got a perfectly clear explanation. (Or maybe I'm too dense to understand it.)

If anyone here has more direct experience with this guideline, especially from the App Store review side, I would like to hear it. I would rather understand the policy than just guess at it.