Capt Kremin, thanks for your reply.
You say, “The track into the SIO was programmed by the FMC or the available autopilot modes. We know that because it flew a straight line to the south.”
What flightpath and endpoint are you proposing?
Do you know what happens when a B777 flown on autopilot in LNAV, encounters an end of route, whilst tracking south on the last leg?