The fact that it's unique/monopolized doesn't mean that competition is hampered. The building (or land parcel) at 100 1st Ave does not provide a service that is ubiquitously needed by almost the entire populace.

If anything, this strengthens the argument. You can buy/rent/... a different parcel nearby, and this only affects you and your planned use of the building. But you can't switch to a different road network, and this affects everyone in their daily life.

That said, I also agree with the sibling post that this is also a problem, just of a different kind.