FATBUS
Yes Pilots need to be wary of "scheduled" and "planned". If the schedule DXB-JFK is 12.40hrs then in theory EK should be keeping an eye out on the average block time to ensure it's a good and if required adjusting it on a seasonal basis (due to slots etc) I guess with JFK taxi times the one more likely to be a problem is JFK-DXB.
On report on the day of the operation the flight time might be showing 13.10hrs but the FDP calculation I believe is based on the "scheduled" time of 12.40hrs because who know's what will happen en route particularly on such a long flight (yes it's more than likely it will end up with in advertant use of discretion).
Personally if I were EK i'd muster a standby crew somewhere in Europe so a plane could drop in for a quick crew change. One of the posters mentioned he got off and caused a 7hr delay in DXB, this would be a way of reducing that scenario. If I was a punter i'd prefer that.
I also think it worth pointing out that the flight departs DXB at 0200LT I believe so it's definately a "long haul" schedule