I didn’t understand the “brown paper bag rule” thing. It looks like this sort of sorting behavior is just universal.
Darker than a “brown paper bag” is “too dark.” Not allowed in black high society (among women).
Several years ago Don Imus had an author on (many times) who wrote a book about black “high society” in this country. Wealth created in the late 1800’s/early 1900’s that endures today.