2 year old survival world and I have now spent 5 earth days and searched over 50 sunken ships and there is no moss block in loot chests. The loot chests are the exact same combos as 1.15, 1.16. I feel this is an oversight for established worlds when it comes to moss. I found glow berries in my first new chunk mineshaft chest. Also, I have yet to see any bedrock YouTuber show they have found moss block.