Most natural blocks added before 1.16 can be used in the Material Reducer, but it has not been updated to allow for newer blocks as should be expected.

These blocks can not be used in the Material Reducer despite all other similar blocks being able to be used:

Amethyst
Ancient debris
Basalt
Blackstone
Calcite
Coarse dirt
Copper ore
Deepslate
Froglight
Glow lichen
Hyphae
Moss block
Mud
Nether gold ore
Netherite
Nylium
Podzol
Polished stone
Polished stone slab
Raw copper
Raw gold
Raw iron
Rooted dirt
Sculk
Shroomlight
Soul soil
Stone slab
Stone stair
Tuff