All other crimson and warped wood items use the new Nether Wood material, but stems, stripped stems, hyphae, and stripped hyphae use the basic Wood material.
Some visible consequences of this include these blocks causing note blocks to play the wrong instrument. In addition, they can catch fire from lava (though they don't burn away).
Comments 3
Materials aren't 1:1 with gameplay. If you look where blocks are assigned materials in code, they use the Wood material.
Cannot reproduce. Nether "woods" don't burn, while regular wood does.