In buffet menu, there is no option for all biomes. This was a feature before in Custom world (pre 1.13) and I had not seen anything about getting rid of it.
Not only do I think this is wrong, but I strongly desire more customizability to my worlds like there was before 1.13.
This report is invalid since it's a feature request. The customized world type was removed to be reworked in 18w06a (see MC-125172). Buffet was re-added as a more limited version (if I recall correctly, it was added specifically so that a single-biome world could be created still). Unfortunately, I don't know what the current plans are for re-adding customized worlds.