It does not
They denied because of the 390-rule: It has to be on Aegean ticket stock. Guess I will try again tonight, maybe another operator may be more forgiving..
Alternatively I could try to get a refund through the OTA; its a flex ticket thus refundable for free. And then rebook on the Aegean website. Also it seems that the Aegean website lets me rebook the flight for free online, eg to an earlier feeder flight. With some luck that would change the e-ticket to 390...
Its still weird though.
All flights in the booking are A3 coded. Normally the marketing carrier of the first segment is the one issuing the ticket, so this should have been A3 (390-xxx).
Is this a matter of the OTA doing tricks, or Aegean themselves routing bookings through Olympic for whatever reason? When looking through the Olympic website it even becomes clear that they even use the exact same prices, as well as the same booking engine as Aegean. The website is a copy of the Aegean one with a changed logo!