Minecraft wiki entry for Diamond_Ore, associated text: "[MCPE-127555] Diamond ores are very rare - Jira" – Mojira, May 6, 2021. "Alright, since people are still questioning why, this is how the diamond ore generation got reduced to literally half of what it is intended to. The 'count' was set to 4 instead of the default 8 in the diamond_ore_feature.json file, which is likely caused by copying the same files from the experimental caves behavior packs."