Phil has always been very precise in his twitter posting, especially when he posts while filming. He takes great pains to not "lie" to his followers. His posts are "obtuse" enough to require careful thought to decipher his meaning. I have no doubt that if Phil says he is "jet lagged," then he has crossed enough time zones to really affect his rest cycle.
If a person flies 8,10, or 12 hours, you will be fatigued when you arrive. If one was flying N/S, then you arrive in the same approximate time in the sun cycle as when you left. If you fly to the east, then you have all those hours PLUS the hours for all the time zones you fly across. So you could arrive at you destination, feeling like you have been flying 12, 14 or 16 hours, with respect to the sun cycle.