Easy explanation for that one
there basically are no (or very little) ethnic women here, compared to ethnic men
I'm sure you've seen the news
The immigrants coming here, is just men (which many of us in British incel community are naturally angry about). The few ethnic women that come here also, obviously they partner up with their counterpart male very easily, because there are about 10 of them to choose from! Trust me the FOB ethnic female with white man is basically non-existent.
Easy explanation, like I said, don't look too much into this study. If it were a study for only ethnics born in UK things would be much more even, actually the ethnics might even be able to beat out the blacks.