Great Harbringer weapon choice question

Hello

Every Great Harbringer has an option to change "any" of his weapons to missile weapon. But since it has only one weapon, this would left him without melee weapon ( is that even possible?). I guess that there is a mistake. Comparing to Greater Harbringer, which has 2x weapons, Great Harbringer either also should have 2 weapons, or got "Upgrade with" instead of "Replace one"