A student or scholar must have been a resident of the treaty country prior to entering the U.S. for the provisions of that treaty to apply. The key factor is the residency and NOT citizenship of the individual. In most cases, the person will be both a citizen and resident of the same treaty country. However, it is very important to determine the country of residency in order to apply the proper treaty benefits.
Again, treaty benefits are tied to the residency of an individual immediately before entering the U.S., not the country that issued their passport.