Incendiary Airburst Launcher - Progression

For the assignment “Deal damage with the incendiary airburst launcher as support” /2000 it appears it only registers damage for the direct hit (doing around 10-15 damage) as opposed to the area of effect damage, this makes the challenge practically impossible as the launchers main damage comes from the burn effect of the actual “incendiary”.

it takes around 150-200 direct hits to complete challenge taking hours and hours. I believe this must be a bug as the weapon is an area of effect weapon not a direct hit weapon?