[leijurv]

Not quite a shortcut, it was actually to patch a bug in vanilla minecraft that causes desync, see https://news.ycombinator.com/item?id=29621262 And it may seem silly that it tells you that it's block type ABC, but the reason is to tell your client to put it back as block ABC, instead of air. (in other words, it has to "undo" your client claiming to have mined that block [which replaces whatever it is with air]).

[rvnx]

I don't know why the server would give information about far-away chunks (maybe some tolerance due to possible desync why not) instead of an error code "you are too far" :/

[leijurv]

Well, read https://news.ycombinator.com/item?id=29621262 if you want to know why this ended up happening :)