The lumber produced by the starting scenario are the 3.841 version's generic "slender tree trunk", "board", "log".
The felled trunks seem to have spawned correctly: "pine tree trunk", yet they produce generic "log". Any such log chopped in to blocks produces generic "block of wood", chopping a "pine tree trunk" does work as mentioned; producing "pine wood block".
Edit: updated subject. It would seem that all pre-generated lumber is generic. Visiting villages for first time, any existing stock of boards, slender trunks et cetera are generic type.