If you don't have the fuel to be 2000 feet off your optimum, you haven't got the fuel to go. International flying requires a 10 percent buffer for that portion of flight 2000 feet low doesn't push up your fuel burn by 10 percent. Not even close. Furthermore, once you are past that portion of the that 10 percent is no longer in the required (IOW's, now its yours to burn....)
Assuming they were doing some sort of rerelease flight plan, they should have gotten over release point and made their decision at that point. But again, that doesn't seam to have happened here.
Now they have to defend themselves from a government beaurocracy that is acting with the benefit of 20 20 hindsite, and they are gonna scrutinize your decisions. On SOOOOO many levels this was a foolish decision, that appears to have been carried out for the very LEAST important reason (Economic)
Cheers
Wino