Using your logic then China is a Nationality and the Chinese are not an ethnic group. China has many ethnic groups within their nation just like Nigeria. No one bothers to refer to Chinese by a specific ethnic group in their country. They are just all Chinese.
The current genocide against the Uighurs shows that the Han (the majority ethnic group) is not the only one, and that ethnic differences are very much a fact in China. And it was your logic that said nationality = ethnic group, when you said that Nigerian, French, English, Spanish...were ethnic groups, as opposed to nationalities.
Anyway my post was to question what that other breh was saying, since ADOS don't consider other Black people as African-Americans (which is what you say), so they cannot be used as an "example" of African-American diversity, as opposed to Latinos, who come from various countries and are all considered Latinos.