Resolved in 1.21.6 and above.

The 1.21.5 version of Terrestria, but since it's fixed for the later versions (1.21.6) then I think it's fine

Ahh, yes in that case when you move to 1.21.6 or above this should be resolved. 1.21.6 uses the WoodType for more things than older versions did, so it was time to make that leap.

What mods? What version of Terrestria?

I ask because you cannot be correct about this. Here is what the WoodTypeBuilder.copyOf(WoodType) method does:

	public static WoodTypeBuilder copyOf(WoodType woodType) {
		WoodTypeBuilder copy = new WoodTypeBuilder();
		copy.soundGroup(woodType.soundType());
		copy.hangingSignSoundGroup(woodType.hangingSignSoundType());
		copy.fenceGateCloseSound(woodType.fenceGateClose());
		copy.fenceGateOpenSound(woodType.fenceGateOpen());
		return copy;
	}

This method does not copy anything which would be incorrect for a new WoodType. In fact if we did not use the method, we would simply set all the exact same values ourselves.

That being said, the source code you cite is very new. We used to actually set our WoodTypes to a similar vanilla type. So my guess absent contrary information is you are using an older version (1.21.1 or 1.20.1 probably) which actually uses a vanilla WoodType.

All of that being said, I don't intend to go back and change the WoodTypes and BlockSetTypes all over the place for a few mods that make silly assumptions about how WoodType is used by other mods. It's just too much work for too little benefit. Starting with the pre-releases of 1.21.6, this is all done basically like how vanilla does it.