Minecraft 1.16.5
Forge 36.2.2
Greek Fantasy 16.4.18

You currently can't craft basic vanilla wood items from the Greek Fantasy wood types. ie Olive/Pomegranate planks won't make some things like: chests, signs, fences, gates, buttons, pressure plates, & boats.
Options that I can see:

• Super easy way - leave it as is.
• Medium way - have them craft into the vanilla items.
• Hard way - make your own versions for each wood type.

EDIT: Added specific wood type craftings missing to save you the effort

I tested the latest version of the mod and olive/pomegranate planks are usable for chest, stick, bed and any other recipes that use the minecraft:planks item tag.
Wood-specific items like signs, fences/gates, boats, etc. are on my to-do list but I was waiting to see if anyone really cared about those. Looks like someone does, so I'll add them soon :)

Thank you! Your mod is a big part of my pack that we are nearing release for. :)