The runtime mirror list is created from the custom mirrorlist if it exists or the default pool.
The custom mirror list is created from the default pool.
- runtime mirror list: /etc/pacman.d/mirrorlist
- custom mirror: /var/lib/pacman-mirrors/cutom-mirrors.json
- default pool: /var/lib/pacman-mirrors/status.json (same as https://repo.manjaro.org/)
In theory, if a user runs pacman-mirrors -f before pacman -Syyu they should, in most cases, get a reliable repository. imho, it doesn’t make sense to run the systemd timer pamac-mirrorlist because the state of those runtime mirrors may change before you actually run the update.