UnityPlayerActivity.onBackPressed issues

Android. Not sure if specific OS versions matter.

We are watching in Update() for
if (Input.GetKeyUp(KeyCode.Escape)) { /* handle back navigation */ }
Normally, this works out fine.

When the app is loading (Unity splash screen), hitting the back button will close the app
When switching between scenes, sometimes spamming the back button will close the app (or timing it perfectly.)
When going to a web page with multiple browsers installed and none selected as default, hitting back twice before selecting the app in system “complete action using” dialog will close the app

And the same thing in potentially other places, in what seems like places where Android might be switching activities.

We’d prefer the app required a confirmation to quit or did nothing in these cases.

Does anyone know what UnityPlayerActivity.onBackPressed is doing?
Is there something in the AndroidManifest.xml I can set to fix?

Unity responded to my bug report saying this was intentional.