This time they're rewriting the block ID system, which they didn't touch in either 1.8 or 1.9.
They're also running out of block ID's so if they don't do it in 1.13, they wouldn't be able to add in any new blocks. Not to mention the new block ID and command system being way less confusing to new players, stepping away from numerical ID's you have to memorize, and giving mapmakers a ton of new stuff to mess around with because the command system is being streamlined and optimized for easier and mroe player friendly use.
Such a waste of time...
Also, Koi, are you ever gonna update that OP? you've kind of been abandoning this thread, and it's a very poor source of update news as it is now.
But is the frame rate actually going to increase and stuff? I know this whole update is optimisations and stuff. Also, Dinnerbone FINALLY gave a time-based estimate for the first 1.13 snapshot - in "at least a month from now", which means, probably at least November.
Also yes the OP should be updated more. It sucks that this is the "official" 1.13 source yet it's so out of date, especially given that any attempt to make another 1.13 thread is immediately closed.
I am not sure why they need an entire update for technicalities. Didn't they already do a MAJOR internal re-write during 1.8 and 1.9, which is why those updates took so long? In the 1.8 snapshots new content ground to a halt for about four months whilst they focused entirely on re-writes.
How is it that the code is still extremely broken even after two major re-writes? If that's the case, I'm not even convinced THIS one will fix the spaghetti code of Minecraft, and many of these changes seem BACKWARDS (/gamemode 1 is no longer accepted, now have to actually type /gamemode creative).