[2021] Nataruk weapon mod's bug?

This is not actually an explosive weapon. It doesn't have a radial effect on the point of impact, which is what Firestorm would affect. What it does is shoot "wide arrows" in much the same way that a Plasmor shoots "wide bullets".  Try it out for yourself: Shoot the ground near an enemy and you will find that there is no effect on target at all until you get VERY close, and that "near misses count as hits" behavior holds true at any range, it's not because the arrow hit near them.