Specifically, that it needs to be planted in 2x2 patterns. It does plant the saplings, but single saplings won't grow.

Dark oak isn't alone in that requirement, but it would be nice if at least all the vanilla trees worked.

I solved this with spruce trees on my server a while back. You declare a working area for the planter robot which has 2x2 patches of dirt separated by a block. The planter should place saplings only on the dirt, giving you the 2x2 pattern you require.