Pretty sure it won't. I bet it's going to use a self-made system upgrade facility and not rely directly on pacman either.
pacman is great for its intended use-cases, but it's not a package manager you want to use with no supervision of an experienced user. It may even silently leave a package in broken state just because the rootfs went full during the upgrade.
And at the very least, pretty sure they're not going to use actual Arch system repos but roll their own.