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

[QuintusSertorius]

It is also possible that owning a settlement, by M2TW engine alone, converts the province to the faction's "religion/culture"...

I suspect that is what's going on in my case. A hardcoded "religious conversion" over time.

EDIT: Just to report, Hellenistic Polities is still rising in all my settlements. At 33% in Massalia and Emporion, and 28% in Alalia. It's even risen from 9% to 10% in newly-taken Nora.