Maybe I'm reading this incorrectly but it seems like the code ignores the amaranth rarity config option (which we have set to 1). Additionally, I have been unable to find any amaranth despite extensive searching. Nobody else on our server has come across maple, silverbell, or tiger trees either (which all seem to share the same tree generation code).

Our pack is a slightly modified FTB Beyond with Realistic Terrain Generation added (I doubt that's affecting anything but it's possible).