I have not heard that. In fact, the black guys I used to work were pretty neutral about African blacks. Unless they were compromising their position of victimhood.
I was just passing on what I have heard to be a generality. I, too, know American blacks who are friendly with African ones. However, people who happen to be of the same race don’t automatically like each other. There have been times in history when American whites hated Southern whites, British whites, French whites, and German whites. Koreans don’t like Japanese much. Tutsis certainly don’t like Hutus, etc.