To be fair most Rodorians would presume that pretty much any human of a distinctively different ethnicity native to the areas between Rodoria and the deep Balazth and Malith (both of which have very distinctively different human inhabitants similar to negroid races from Earth) is Catolohne. To almost anyone that has no particular interest in what lies beyond the borders of their own nation, "south" is pretty much synonymous with "Catolohne".
Also to be fair, most of the monarchs throughout the history of Rodoria would probably also have protested against the Zerulic-Pelgaidian arranged marriage, which is definitely not something one would ordinarily see there... at least not obviously so, and not among highborn nobles bound to make a spectacle out of the event.