adb is a developer tool. You need a tethered and trusted computer to be able to transfer an app using adb, and you need to enable "developer mode" on the device, which is an arcane dance that involves navigation through an obscure tree of settings and then quickly tapping a mystery spot 5+ times. Google
can't block adb, because that is how Android apps are developed and tested, just how Apple cannot block their developer tools from being able to transfer apps onto an iPhone.
This is so far from a realistic and acceptable substitute that I question the honesty of anyone who claims that "adb will still work, so no problem!"
I hope that explains my seemingly critical omission.