Hello,
in release notes I see, that this was fixed:
GI: Fixed broken baked shadows with speedtrees
Still not sure how it may work. If I add speedtree to unity terrain baked shadows are missing on terrain.
If I add speedtree as individual gameobject, shadow is baked onto terrain.
Not sure what is bug or baked shadows with trees inside of unity terrain are not yet supported.
Regerds
Peter