Probably wrong context, but the more code I wrote, more I like the these `Has`+Noun style naming than just Noun. Reading `HasChildren` will give you a clearer expectation of what the function would do and return, while `Parent` gives far weaker indication.

Maybe they thought the same when they were designing the protocol.

Also, in the context of email, given the size of each mail (including headers and body), these bytes "waste" maybe insignificant.