"Casual Diversity" Depends on the Unseen Work of the Author

Librarian and blogger Betsy Bird recently issued a call for books featuring "casual diversity," or a list of children’s books in which "diversity is just a part of everyday life." Here's my two cents:
Even (perhaps especially) in such “real world” books featuring characters with different ethnic backgrounds, the author and/or illustrator should think through carefully how that heritage would shape each character. Perhaps none of that background work that has informed the author’s imagination will be obvious to the reader in the final story or art, but our reflection, personal experience, and research will all affect the characters' depictions–and the child reader–in subtle ways.
Throwing in a character of color here or there to make your book more multicultural isn't a shortcut to representing all kinds of children in the real world. As authors and illustrators, the onus is on us to do the unseen work of listening, learning, and understanding, especially because we write for children. What is "under the waterline" in us is bound to be revealed in our stories, and will inform what is "under the waterline" in our child readers.