(THIS ISSUE IS FOR 1.16, BUT I COULDN'T GET THE OPTION!)

The issue is when you use a data-pack or mod, I can't seem to change the Spruce, Jungle, Crimson or Warped Planks output. 

When using a data-pack, "minecraft" as the namespace, and changing the recipe to  2 planks instead of 4 planks as the output, it doesn't change, unlike oak, birch, acacia, and dark oak wood.

The mod attached is for Forge, but this can also be done with a datapack! (1.16)