With widebody aircraft at such high TOWt's it is often the case EVEN WITH THE CORRECT CALCULATION ENTERED INTO THE FMGC to rotate in the last 1000m of a large international runway. The crew were expecting of course to rotate well down the runway as all previous flights would have done. To put to bed the issue of the rotate speed awareness, it is more a factor of how long it took them to get the intial acceleration going, that would be more of a tell tale that things were not going as planned as the slow Vr speed would only be picked up too late as happened on EK407 when TOGA was THEN applied. Having said that, in 25yrs of flying, I cannot say my personal accelerometers are that good to assume the intial acceleration is always as it should normally be.