CO-Mike does the same thing on its GUM-YAP-ROR-GUM flight 955.

I think they do it so they don't have to give FF miles for the back-track part of the flight. If you fly EWR-DUB-SNN you don't get the extra miles between DUB-SNN (122 each way) unless you connect. No change in flight no extra miles.

Also if you take flight 7 IAH-NRT-GUM you get the same miles as CO 1 IAH-GUM or 7447 and you go from a 777 to a 737-800 in NRT but the same flight number.

The games we play for miles.