I do find it odd if someone isn't attracted to their own race. Not wrong, mind you, but a bit strange.
People are narcissistic in nature and are naturally attracted to people that have similar features to themselves, even subconsciously. I would have to assume that not being attracted to your own race is fairly rare.
I suppose I'm also assuming things a bit in that not dating your own race doesn't necessarily mean not attracted to at all. Considering who you date can be largely influenced by environment and location.
I certainly don't consider it weird and neither do the people in my life. It seems to me that it's pretty normal to date outside your origin and i don't get why it wouldn't be. I understand your confusion, where did you hear this?