As I said before it was probably a confusion on the different uses of the word planned.
The schedules are planned over 6 months ahead and as a compromise use something like 75% probability winds They also have to allow for taxi time etc. This will mean that on the actual day of the flight there is a 25% chance that the flight may take longer than the published schedule.
Some less reputable airlines may ignore this and make the flight times fit a suitable FDP when there is little chance of the flight being completed without the use of discretion. In the UK the CAA are supposed to monitor for excessive use of discretion on any particular route and then have the power to get the airline to produce a more realistic schedule. Thats the theory any way.
All the best
Don