I remember the first time hearing both of those albums. In fact Eminem's first album may have been that last rap CD I purchased. I still have my copy of the first Beastie Boys I enjoyed the humor in them. Both artists did something different with the form. By the time Slim Shady came around rap had already ben coopted, so I'm not surprised Em is from Kansas.
Langston Hughes is from Kansas and he is perhaps the most recognized figure from the Harlem Renaissance.
People create fictional origin stories for a variety of reasons. Sometimes they say they are from some larger city when they were really from a smaller nearby town no one has heard of and it is just easier to say the more recognizable location.
Sometimes when people ask where I'm from and I'll just say New York City. If they probe further, I'll say Harlem. If is not unusual for white person to say. "you don't seem like you are from Harlem." But those are people operate on stereotypes (@Pioneer1) and I do not fit many people's (Black or white) stereotype of someone from Harlem.