[DA 2.01] 'Gravity Accelerators'-bonus isn't transferred on trade

I kept on wondering why my hulls suddenly have only a base movement of 4 instead of the ususal 5. I went back to some savegames and checked when this was lost, and it seemed to occur after I traded the planet (where I build this Trade Good) to the Yor (their final residence)

The strange thing is that, during the same diplomacy-conversation, I traded this Trade Good back to me, and would have expected that it might be taken into my racial stats. This didn't happen.