World Chunks Don't Seem To Buffer and holes are back. As you can see from the attatchment below the holes of the world are back and have been since 1.9 but, in 1.13 it's a bit different. Not only have the holes come back for 64bit 1G ram argument users but, when joining a vanilla world it can take up to 30 seconds before you see chunks.

There are other issues like flying around it can't keep up and doesn't seem to buffer the chunks f3+a seems to fix it within a minuet(no joke actually 60 seconds).