Title. Every biome file (speaking of the biome files used in datapacks) contains a list of features that can spawn in that biome. Deep Aether's biomes have all of Aether's ores, but the gravitite_ore_buried feature is missing from the list. This causes Gravitite to be notably rarer in Deep Aether biomes compared to the rest of the Aether. The fix should be simple, fortunately: Just add it to the list like the normal Aether biomes do, right above the regular gravitite_ore feature.

To be more specific, I'm referring to Deep Aether 1.0.8 on 1.19.4. This might be fixed in other versions; I haven't checked.