They are arguing over whether the presence of a competitor within 1/2 mile counts as competition even though the competitor has not actually started service to the customer.
i.e. does the customer actually need two services? Or is the presence of another one very close by, enough to be considered as competition? (The assumption being that they would/could expand to the customer.)
Better title:
FCC can define markets with only one ISP as “competitive,”, if there is another ISP within 1/2 mile, court rules