Yes, as peeps have stated already, FD messed around with and messed up, the raw material grading. Selenium is a g2 in a g4 position at the trader for absolutely no good reason. It cannot be obtained from g4 sources (needle crystals/crystalline shards), but it can still be obtained from any G2 source (primarily Crystalline fragments at volcanic sites and mesosiderites under the old planetary prospecting model).
Since we're sharing I actually enjoy my selenium method. I go to Prthi 2A and get in the SRV, make like Ken Block and shoot every rock I see. In about an hour I've collected over 100 selenium usually. Favour mesosiderites as they are the primary g2 source, but any rock can contain selenium on prthi 2a, it also seems to have quite a few metallic meteorite spawns which will give you a lot of extra antimony while you farm your selenium.