When Klaus breaks down a tree by walking over it, the tree usually don't drop the logs it should. As to my observations it has been since Klaus was added to the game.
However, I just saw that when a tree in the Ant Lion's desert was crushed down by Bearger, it also didn't give any logs, and only one birchnut (instead of two).
Anything else than trees (boulders, buildings ect.) did drop all the expected loot.
Steps to Reproduce
Default world settings, make Klaus walk over trees, or a Bearger in the small desert biome.
This issue has not been confirmed by a developer yet.