Actually, the name started as Art Corvelay. They were waiting in the building for the woman and cooked up the name as someone they were VISITING in the building to have lunch with. There would have been no reason for George to have a different name. (He did, however, claim to be an architect.)
They were trying to come up with a name and George said, "Art Core." Jerry looked at him and George added, "Velay. Art Corvelay." What did he do? He was an importer. Just imports, no exports? All right, he's an importer/exporter. Later, Elaine changed the name to Art Vandelay for no apparent reason.
Of course, that led to Vandelay Industries (and latex), and to the Marissa Tomei episode in which Art Vandelay was again an importer/exporter. George also pretended to be an architect in the episode where he races Duncan, his rival from high school. And he complained, in "The Marine Biologist" episode, about Jerry telling the woman that George was a marine biologist instead of an architect. ("You know I always wanted to be an architect.")