alt Hacker News> I think "storing deltas" based on seed is largely how Minecraft saves the level already
This is not the case, level data is stored in full. One reason for this is that level generation is pretty slow (compare the time it takes to create a new world vs. load an existing one); another reason is that it changes between versions.
Fun fact - bedrock only saves chunks modified by the player because consoles are much more restrictive with save file size than PC. If the world gets too big, your save is effectively lost.
Java does save chunks after generation, likely due to world gen updates not seamlessly transitioning with older versions of the game and PCs not caring about save size.