I don't think its about being Asian per se. I think it has to do more with height preference. Asians in general are not that tall. There is also this notion that Asian men give off this inclusive vibe that makes women think that the men would never date outside his race.
You could also say that negative Asian men stereotypes (ex: Asian men are asexual, not attractive, etc) are a factor but I think that notion is slowly dying down in the media (just look at Fast Five and Fast Six, etc)
You left something out ::snicker::
But yea I've noticed that it's a lot harder for Asian men to date outside of their race compared to females. Pretty interesting.