Attaching an example of the bug
This isn't really a bug: it's referring to how the Desert preset is configured, compared to how normal Minecraft desert terrain generates. He is proposing that the Desert preset be changed to "3;minecraft:bedrock,52*minecraft:stone,3*minecraft:sandstone,8*minecraft:sand;2;village,biome_1,decoration,stronghold,mineshaft,dungeon" in order to mimick the normal terrain.
I believed this to be a bug. Perhaps I misunderstood what barriers were for...
This bug is still present in the 1.14.2 release.