I think the implication is that people are interested in their own race by default and everything outside of that is notable/unusual.

Not sure I buy it.

No the implication is people find people similar to the people they interact with regularly attractive by default. This doesn't preclude people from liking other types of people, but it's not common for someone to grow up surrounded by certain types of people and find none of them attractive.

I don't think that's obviously the case. What _is_ the case is most people dating people who are 1. in close geographical proximity 2. in a similar socioeconomic position, not necessarily because they prefer that, but because that's the most natural way (at least historically) to find someone to date.