This is another myth IMO, the "racial trait" of asiatics being that they "pass" better, it's not real.
It's another illusion, one that's borne out of unfamiliarity because different species have different secondary sexual characteristics, the same is true of dogs and horses, like how westrons cannot readily distinguish between gooks/nips/chinks/seamonkeys whereas for the indigenous yellow it's the opposite. The "passing" is the same result of this; yellows in general look "the same" to the European eye, hence the man/wahmen blend.