"systemd" is the init system, therefore anything that has it in the name is part of that init system. See also journald, which nobody mentions as being part of

"systemd" is the init system, therefore anything that has it in the name is part of that init system. See also journald, which nobody mentions as being part of the init system even though it's more tied to it (is it even possible to have systemd without journald?) If they want to change that perception, they will need to change the name (and hopefully stick a stable ABI around it, but that's unlikely to ever happen).