Sounds like bias to me. We're genetically hard-wired to be attracted to those different to us.
For example, I don't think that (on average) the locals where I live are particularly beautiful in comparison to other countries, but a lot of foreigners seem to disagree with me.
I'll look for better (primary) sources when I'm not on my phone if I remember. I vaguely remember seeing a bunch of stuff about how humans naturally gravitate towards genetic diversity, unless there's some roadblock preventing it. I don't have a source offhand though so until or unless I find one, remember to add your salt :)
For example, I don't think that (on average) the locals where I live are particularly beautiful in comparison to other countries, but a lot of foreigners seem to disagree with me.