Is everyone coming from the UK tested on arrival in Greece? If tested, do you need to self-isolate?

The section on "Protocol for air arrivals" at https://travel.gov.gr states:

Depending on their QR code/confirmation, travelers are directed either to the screening area where they will be tested for the new coronavirus SARS-CoV-2 by a trained health team or to the exit (to baggage claim area or passport control).

Is the criteria for testing publicly available or otherwise known? Are arrivals from the UK subject to testing?

It also says:

The test results are expected to become available within 24 hours. During that time, passengers who are tested are advised to practise social distancing according to local guidelines and self monitoring for symptoms that could indicate COVID-19.

Does this mean you don't need to self-isolate if you're tested, and are free to go out even in the first 24 hours provided you don't develop symptoms and practice social distancing otherwise?