I agree, but its fact that the planning stage is one thing and the operational phase is another. EU-OPS and most world regulations rules different things for each phase. There are different requierements for each phase. The planning is based on all available info to get the closest estimate to what the operation is going to be like and have your safety limits properly set. In the operation phase we need to be considering many more factors many of them that can't be even imagined in the planning phase.