Clearly what was meant was that an average white person who was asked to imagine an attractive potential partner, would image a white person of the appropriate gender. Thus asians do not look like the image of "imaginary attractive potential partner" of most people (in the US). This doesn't mean that asians are unattractive. Just that most movie stars are not asians.

White-Asian marriages are something like 80% white male/asian female, 20% white female/asian male.

"Asian" is not an indicator of unattractiveness; "male Asian", on average, is.