Assignment for 5 Shotgun Kills without Reloading

One shotgun assignment has a task stating "Get 5 shotgun kills without reloading".

I killed 3 people with my shotgun, killed a tank with my RPG and reloaded my RPG, then killed 2 people with my shotgun, and the assignment indicator in the top-left only said I had 2/5 shotgun kills.

I think reloading other guns (secondary, RPG, etc) incorrectly counts as a reload for this challenge.