I am not quite sure that I understand any of the responses except consideration for runway conditions at a higher weight but this is Munich. Doesn't it have 4000m runways. Perhaps on a very few types this could come into play or in very poor conditions. I suspect that LH is landing at Max Landing Weight here on most winter days.
As an interesting question, ask the person who assigned this project, how much fuel would they typically tanker to this airport and if they would bump it for contaminated runway conditions even if the performance figures show it is within limits. If the answer is....they would not take the extra fuel, ask if they would still take in an equivalent amount of extra payload.
Someone talked about the requirement to de-ice, but at -15, won't most aircraft get frost anyways during an overnight stay.
On the plane I have flown, frost on the bottom of the wings from fuel is not de-iced for most aircraft unless it is significant(more than 3mm). If you are going to get frost on the bottom of the wings from cold soaked fuel, won't it happen even if not tankering as there is always some fuel in the tanks.
Fuel freeze temperature does not need to be considered because the example says that the OAT is a constant -15 degrees Celsius.