What has a METAR or a TAF got to do with a particular runway? Meterological sevices work in True. How can they use anything else? High level winds can cross areas of rapidly changing variation. Magnetic is something that is (or used to be!) required for navigation, not for forecasting the weather.Simply think of all Met products, including TAFs and METARS, as being produced by a meteorologist, who does not know anything about variation. ATIS and winds given from the tower are an ATC product with variation applied, as the navigation element is relevant.
It is immediately obvious that this is the correct system when operating in parts of the world with 20 or 30 degrees variation. If everyone had modern naviagtion equipment, then we could make True the primary reference in all circumstances!