Right so this is checksum based?

correct

Are there plans to only store delta changes for files (i.e. store the changed byte instead of the entire file)?

Long story short, no 😞
Basically delta changes are not scaleable. and work only in text based files, see git, and breaks very quickly when large files are involved, see the fun of git-lfs ...
Does that make sense? is there a specific reason you are thinking about byte granularity ?