You're entirely right. The anti-Asian bias would probably (as suggested by the article) also impact populations with the same socioeconomic detriments, examples of whom can be seen among Vietnam War refugees and subsequent South-East Asian asylum-seekers/immigrants more generally, as you suggested.

So by penalizing the whole band of Asian races to even out admission, a whole bunch of materially disadvantaged Asian populations end up less favored than their African counterparts.

It's an unfortunate state of affairs.

Actually, I forgot to add that it can be bad as a whole for Chinese people too if they're stereotyped as rich. There are plenty going overseas to study who are pretty much in poverty too or even those born here with a Chinese background that are poor.