My luck may just be incredibly bad, but I did not touch fates before the relic quest came out. I ground out every FATE needed for Shared FATES in Kozama'uka, and I received ZERO demiatmas from start to finish. That's hours and hours of just fates and waiting for fates to spawn and nothing else. The drop rates genuinely need some sort of pity system, as this kind of drop rate is unfathomably bad.