"Muluna, Moon of Nauvis" is a Space Age mod that adds a moon you have to progress through before moving on to other planets. You can't initially drop any items onto it, and there is no copper available, making it impossible to craft Blueprint Shotgun's ammo when it would have been the most useful.

Since Mulana does have an alternative way of making copper cables, changing the ammo recipe to use that instead of copper plates if Mulana is installed could be a good way to add compatibility with it.

You're incorrect on one statement. Initial cargo drops are only banned on Muluna when a setting under the "Roc's Hard mode" designation is enabled. This is not the typical game experience. However, since Roc's hard mode planets typically allow the drop of construction robots, it makes sense for this mod to also allow the drop of blueprint shotgun ammo via PlanetsLib's interface.

I've added Blueprint Shotgun's items to the cargo drop whitelist of PlanetsLib in 0.2.13, thanks for the report