Well, Earthdawn and Shadowrun have not been entirely consistent on the Loremaster topic. Earthdawn books described Vasdenjas as "Loremaster of Barsaive." That is, the Loremaster of the Council of Dragons of Barsaive, while there were Council of Dragons of Vasgothia, Cathay...
Shadowrun Survival of the Fittest reads like there's only one World Council of Dragons and one Loremaster.
My pet scenario to explain the difference is that Dunkelzahn "unified the belts" between the Earthdawn era and the end of the Fouth Age. He first won Vasdenjas Rite of Succession to become Loremaster of Barsaive, and then moved to Vasgothia, Cathay and Americas to win other Loremasters' Rite of Succession (or kill Loremasters, which is another way to get the title according to SotF). This is consistent with the fact that Dunkelzahn (and Ghostwalker) moved away from Barsaive before the end of Fouth Age, establishing a lair in the Front Range.