I can't find it right now, but will look around, but there is a sociology paper I want to  post.  Do a quick search and  you'll find that basically it comes down to Asian women and Caucasian men are, as a group, the most accepting of out group relationships, which is why the Asian women/Caucasian man pairings seem to be so common. If I recall correctly, it was the same across most Asian countries.  I think that it said that Asian men are the least open to out-group pairings, followed by African men, African women, Caucasian women, Caucasian men and then Asian women.  If this premise is true, then why wouldn't we expect to see Filipinas, who the study says are more willing to have an out-group pairing, with non-Filipinos?

Interestingly, the study found the same attitude among those of historic Asian ethnicity as among true culturally Asians.

Having spent nearly a decade in east Asia it seems my personal experiences would agree with the study.  I'll see if I can find it.