[Hellenistic Poleis] Can they be upgraded without a Metropolis?

[V.T. Marvin]

There is some small conversion simply from owning a settlement towards the faction's culture and also there should be some even smaller conversion to other cultures resulting spreading from neighbouring provinces. Neither is exactly hardcoded, these values are IIRC set by descr_sm_campaign.xml file. The values we have now are sort of an experiment to see what exactly the results are and might be changed in later releases based on the feedback we will get.