Who cares? For someone like Francis he is both very much so French and Cameroonian, a French Cameroonian. Izzy was born in Nigeria and he grew up some there and New Zealand, which is where he now lives. A Nigerian Kiwi.
Are you implying people shouldn't train or live elsewhere than the country they were born? Or that people should identify souly, if at all as a fighter from wherever it is they train? Many guys train abroad, or train in multiple different countries year round.
Maybe people are multi ethnic, truthfully and people like the push back against this but everyone is multi ethnic...Every ethnicity stems from groups splitting and other groups joining and changing.