Are you saying ethnic minorities in the West are less likely to be WEIRD and hence underrepresented in EA, or that ethnic minorities who are WEIRD are underrepresented in EA? The former wouldn’t surprise me at all, given the significant disparities in income and educational opportunity between ethnic minorities in the West. The latter would surprise me, but I’m not sure how you would go about proving it, since it would require you to already have an estimate of demographics of true WEIRDs, and I’m not sure how you’d go about collecting that. Unless the assumption that any educated person from a Western Developed country is WEIRD, which I would disagree with.
I’m claiming the latter, yes. I do agree it’s hard to prove, but I place high subjective credence (~88%) on it. Put simply, if I can directly observe factors that would tend to lower the representation of WEIRD ethnic minorities, I don’t necessarily need to have an estmate of the percentages of WEIRD people who are ethnic minorities, or even of the percentage of people in EA who are from ethnic minorities. I only need to think that the factors are meaningful enough to lead to meaningful differences in representation, and not being offset by comparably-meaningful factors in the other direction. Some of these factors are innocuous, some less so.
But if you’re interested in public attempts to take the direct comparison route, which I fully acknowledge would be stronger evidence if done well, you might find this post of relevance. (Note I’m not necessarily advocating for the concrete suggestions in the post, mostly linking for the counts at the start.)