As of the latest Preview, it appears that the existing wooden-textured stone-like slab has been converted to the new IDs improperly.
Specifically, "minecraft:stone_block_slab" with metadata 2 becomes "minecraft:oak_slab", rather than "minecraft:petrified_oak_slab".
Expected results
Existing cases of these slabs would convert over to a new ID that retains their original properties, identically to how petrified oak slabs continue to exist in Java Edition.
Actual results
They are converted to oak slabs instead. This is detrimental for structures which used the non-flammability and other such properties of this slab to their advantage.
Comments 7
It would be helpful if you listed the old and new IDs in the Description along with the ID you expect it to convert to instead.
To reproduce, just run /setblock ~ ~ ~ stone_block_slab ["stone_slab_type"="wood"] in 1.20.80, then upgrade this world to 1.21.0.23.
Although, this is probably working as intended according to the changelog.
The id "oak_slab" had already been split from "wooden_slab", as a result, any "stone_block_slab:2" will be turned into the already existing "oak_slab" id
I think the ID should be converted to "wooden_slab" or "petrified_oak_slab" instead of "oak_slab" (this will cause all wooden slabs(petrified oak slab) to become ordinary oak slabs)
Confirmed! This is a parity break with Java that WILL permanently affect worlds if it is not fixed before the 1.21.0 preview cycle is finished. Any worlds that relied on its inflammability will be broken with the update.
It would be helpful if you listed the old and new IDs in the Description along with the ID you expect it to convert to instead.