The data value ID "stone_slab" means different things in 1.13x and the 1.14x snapshots.
In 1.13x it is what's commonly know as the smooth stone slab, a lighter stone with dark edges.
In the Snapshots it has the same texture as the ubiquitous regular stone, while a different block, "smooth_stone_slab" takes on the old appearance of the lighter stone with dark edges.
Both of these versions have the same pack_format number (4), but is is impossible for texture artists to texture "stone_slab" properly for both versions of Minecraft.
Comments 3
> They just use the texture from the full block.
The default pack sure-- but that's not a rule for everyone.
Resource packs aren't constrained by what files and filenames the default pack uses. Artists edit the blockstate .JSON files to apply whatever textures they want to a block, things like random alternate textures, or maybe a different texture to the top face of a block..
In v1.13x the block state file "stone_slab" refers to one block. It's a carved stone slab.
In the snapshot is refers to another block. It's a natural, whole stone.
Whatever textures an artist applies to blockstate "stone_slab", is going to be wrong in one of the versions pack format 4 supposedly supports.
This is actually the case for all slabs. They just use the texture from the full block.