Why testing in Greece?
From the us Embassy website:
Entry Restrictions to Greece Relaxed: As of May 1, 2022, travelers entering Greece are no longer required to display a certificate of vaccination or recovery from COVID-19, or evidence of a negative test result from SARS-CoV-2 infection.
But, on the RC FAQ page it says:
Updated Vaccination Protocol for U.S. and European Cruises Departing on or after September 5, 2022
Beginning September 5, all travelers, regardless of vaccination status, can cruise on the following itineraries, as long as they meet testing requirements to board.(Note: Guests that are not "up to date" on their vaccination per EMA standards will need to take a test onboard in order to get off the ship in Greece and Spain)
It says "up to date" but there is no vaccine required.