This does not seem intended, since the generation settings show all other planet instances having every resource. Nauvis N and S lack coal, and so does Vulcanus N and S. Nauvis N, S, NT and ST lack oil, and the same goes for Aquilo N, S, NT and ST. Seems like some conditions are getting mixed up somewhere in the code.

Oh hey lol, didn't see you post here too! Related: https://mods.factorio.com/mod/intercontinental-rocketry/discussion/67456c6404610a2ed383be74

Yeah, that's an "undocumented feature," also known as something I quickly added to create some distinctions between the different planet zones. At some point, I plan to change how the different zones work, but it will need to rely on a library that doesn't yet exist, one that adds new planet surface conditions such as year length and climate information. I don't want to update this mod until I'm sure that the groundwork for what I want has been laid.

Ah, I see. My confusion then was because it doesn't show coal/oil missing in the map settings menu for the other planets like it does for Nauvis. All Vulcanus and Aquilo instances are listed for coal and oil, but for Nauvis it only shows the ones that have them (as well as uranium).