The author's misuse is all the more painful for being an econ grad student at my alma mater, GMU. A former professor of mine, Russ Roberts (the man behind the Hayek vs. Keynes Rap video), even used a similar example ("Does Ford have a monopoly over the Taurus? Cars? Means of transportation?") to show how little objective utility the term “monopoly” holds. The more narrowly one defines the market, the more one is likely to “discover” monopolies.
Don't forget though, Russ Roberts has an ideological dog in this hunt, and he'd like to recruit more anti-regulation followers, so he'll bend the argument to suit his biases. There is a sorities paradox element to it, but that doesn't mean "pile" is undefined; Ford has a government-granted monopoly - a trademark - on Taurus.
That substitutability is defined in a distributed way isn't a well-formed argument against tying it down in any particular case. Legal courts make these determinations every day concerning the meanings of texts, whose intent can be similarly hard to divine.
We should all have a legal monopoly on who we are. Protection from others pretending to be us. That's all a trademark is. Its not at all like a government granted monopoly that enables a company to be the sole provider of phone or automobiles.
Which we generally call a patent - in my understaning the only real monopolies are government granted ones - i.e you must use ATT for phones, or no one else can manufacture widget X
