It is not particularly intuitive what goes in to a Popen non-shell argument list, unless you are an experienced programmer.  The real purpose of the note is to convey a lot of information about how tokenization works in a short example, and it also demonstrates how to investigate other complex cases the user may have to deal with.  Because of the first part of that (showing tokenization quirks) I don't think it should be relegated to a footnote.

That said, the example could perhaps be reworded slightly to make its expositional purpose clearer.  Suggestions welcome.