Open Jaw is defined in the international contract of carriage. What you propose isn't an open jaw.

Normal Fare Open Jaw means travel from one point and return to another comprising not more than twointernational fare components and the mileage of the surface sector is equal to/less than the mileage of the shortest flown international fare component; the fare is to be assessed as a single pricing unit using half round trip fares, assessed from the country of unit origin.