I'm afraid you missed the joke ;-) While you believe spaces are
required on both sides of an em dash, there is no consensus on this
point. For example, most (but not all) American authorities say /no/
spaces should be used. That's the joke. In writing a line about "only
one way to do it", I used a device (em dash) for which at least two ways
to do it (with spaces, without spaces) are commonly used, neither of
which is obvious -- and deliberately picked a third way just to rub it in.
This will never change ;-)