This seems incorrect, as single saplings cannot produce the equivalent pine trees (at least, that's what I believe they're called in the official decorator documentation) - see MC-175975

Suggested fix would be to make "spruce trees" and "pine trees" two distinct tree species, with different saplings, leaves, logs and wood products. Spruce trees would be the current conventional tree with multiple layers, and pine trees would grow with the clusters of leaves only at the top.