Hi chomwitt, the Hellenic
demonym in Freeciv is currently associated with the modern Greece, featured by the blue flag with white strips, while the nation you picked for GT00 is actually called Ancient Grece
within Freeciv, and has the white flag with green leafs.
This nations nomenclature is intrinsic to Freeciv and has nothing to do with Greatturn. I can pass you request to the Freeciv development board tomorrow, or you can do it directly posting a request at gna.org/bugs/?func=additem&group=freeciv