The figures are not exact for every aeroplane in any particular fleet of course. There are safety factors built in but the idea is for the performance to relate to an average aeroplane flown by an average pilot etc. Given a wet runway, a little slow to get TO thrust set, a fraction late with the rotate, a bit of rudder juggling after V1 engine failure and that 15 feet will feel very, very small if you are at anything like limiting weight.
I have tried it in the sim and have absolutely no desire to experience it in reality.