At the moment the flavor text dialogue is coded mostly for specific factions (the stock ones that ship with the game) and not the traits that those factions posses. For instance it will be like "if: speaker = YOR, then: say this;" It needs to be reworked to instead say "If: speaker is synthetic, then: say this; "
There is default dialogue that kicks in when you have a custom race, but none of it checks for synthetic ability at this point.