There is a transit route at Athens, separately staffed. I used it successfully a couple of years ago and someone will have to confirm it's still there, but I don't see why it wouldn't be. There is/was a security check but not passports.
On another subject, a successful SOF b2b today, very easy. I met someone asking at the gate for a b2b next week whether it was possible; he was wrongly advised that he would need to return through security. Sometimes airport employees don't understand the details!