I'm playing on Badlands map but got lucky to receive an Arbor Acorn on the Printer.
After a few hundred cycles of growing and harvesting, not a single seed has dropped - this is beyond unlikely (the drop chance is supposed to be 10%?).
So this is either a bug or are those simply not supposed to drop?
Can't really reproduce something that doesn't happen :/ I guess plant an Arbor Acorn to grow an Arbor Tree. Tend, supply, harvest for a long time and see that it won't drop seeds.