I updated from the UI. It was uninstalled, not just disabled. After the reboot, it was back.
This is in a snapshotted VM, so I could revert and try again. I did it 3 times. It is repeatable and consistent. Before update: not installed. After update: installed.
Sadly, i've gotten into the habit of checking all components and settings of Avast after an update, exactly because of these shenanigans..