pacman -Syu requires to confirm or cancel installation.
Is there any pacman argument to skip that interactivity and assume ‘yes’ (which is an option with any other package manager I am familiar with [apt, dnf/yum]) ?
is it bad practice to do so (which may be the reason such an option wouldn’t exist)?
After a kernel update, you should restart as soon as possible, so you might want to check first if a kernel will be updated. Or you’re running an important session in Firefox which will ask for a restart after it is updated.
Also unattended upgrades are heavily discouraged. As a rolling release, you can’t guarantee that the configs you currently have for your programs are valid after an update and they require manual intervention. When you do the update manually, so not in a cronjob, at least you know what was updated and can act accordingly.