In service to your point though, Davies … wrote those characters to have those roles. He could have written different characters who would offer some insight into segregation from the other side, whether that meant replacing some of those characters or just adding more. The kid behind the counter at the diner would almost certainly be white, but it wouldn’t be unusual for kitchen or cleaning staff to be black. It’s not that hard to come up with a way to introduce one of these employees, especially late at night when the leads arrived.