Superflat presets can't use blockstates

The bug

When the block data values were removed, and fully replaced with block states, the ability to set the block state on superflat worlds was lost. You used to be able to set the data value in the preset.

This preset is expected to work and place top slabs, but it doesn't.

minecraft:stone_slab[type=top];minecraft:the_void;decoration

No format actually exists anymore to set block states in the superflat preset.

This goes for both the world generation menu, and custom dimensions.