Yes, that was very intentional, for pedagogical purposes.  See the commit note: "Make `return` explicit in the examples, so it looks less like textual substitution and more like a mapping from exprs to an expr."

I don't know that I'd go so far as saying that an explicit return at the end of a function isn't idiomatic.  It's optional.  And here I think including it makes macros much less magic-looking.  This change had support from others in the linked list-serv thread, too.