What I thought: these flights are not open jaw flights but one-way non-stop flights via ATH. The open-jaw flights are "return" flights whereby the return segment does not start where the outgoing arrived. Two examples: [LHR-ATH]-[SKG-LHR] or [FRA-HER]-[JTR-FRA]. There are some who also include "return" flights whereby the return segment goes to an airport near the original deparure one, here would be two examples LHR-ATH-STN or DUS-ATH-CGN.