Does `pm uninstall` also automatically execute `force-stop` and `clear` on a non-rooted device?
force-stop
Uninstalling an app always kills all related processes. Keeping them running doesn't make any sense and can end up in an app crash. Therefore Android kills the app process(es) before uninstalling it.
clear
Clear data and cache directories is enabled by default. It is just the opposite if you want to uninstall the app but keeping data and cache you have to add the option -k to the uninstall command.
clear an system app after uninstall
System aps are located on the system partition which is by default read-only. Thus uninstalling an system app is not possible on a non-rooted device.
If you execute uninstall on a system app only the installed app updates on the user partition are removed and the system app itself is set to disabled. Clearing the data of an disabled app is possible therefore you don't get an error.