How does AC choose which skins go in race?

Hi
In offline races with AI, I get the impression some skins are used more frequently.

I had presumed that the game chose skins to appear in races by random; I'm not so sure anymore.

Are skins chosen according to some criterion: folder name? the "priority" value in the ui.skin folder? something else?

I'd prefer it was just random.

Anyone help? Or am I just imagining the whole thing?