since the aquatic update there has been a bug in on off my superflat world. I transfered that world over from the previous minecraft xboxone edition but at first did not have this issue. the world was set to a superflat swamp biom 50 block of as ground layer.

but the bug is that a part of the biom does not generate and this goes around the whole edge of the map. if you take a navigation map everything inside the shown area is the correct biom but if you go out side that area it just drops off to the regular superflat world. It is super frustrating because I've spend countless hours working on that world.

I think this is a bug because the biom setting I used when I first made the world on the old xboxone edition was large and it was a infinite world. besides that given the image I have linked it does look rather odd and I highly doubt that is intended.

quick summary,

the previous seleced biom and layers from a old transfered world do not generate outside the are shown on the navigation map. it generates more land but not in the desired biom and layers.