That's not necessarily true. Global north labour aristocrats get paid higher, and in this example significantly higher, than global south proletariats because of the global system of exploitation.

Through various mechanisms of global value transfer, labour aristocrats functionality exploit the proletariat proper.

Labour aristocrats are not necessarily being robbed of their labour so much as they are part of the process of robbing others of theirs; and upset that they aren't robbing quite as much as they would like because someone else, the bourgeois proper, is more effective at the robbing.