As discussed in Discord, I noticed that the wood types from Biomes o plenty don't currently work with the IE sawmill (the recipes are not available).
I have compiled a list (newline-separated for each wood type, with each item comma-separated on each line) of the wood type ids which is attached to this issue.
Attached is also a datapack that adds the wood types to the sawmill, that could be used by players until support can be added in IE.

List of wood types:
biomesoplenty_wood_types.txt

Datapack:
ie-sawmill-biomesoplenty.zip