Is It True That Every Premium Economy Row Really Costs An Airline Rows Of Economy Seats?

When United Airlines first took delivery of its Boeing 777-300ERs in 2016, these aircraft were equipped with 60 Polaris seats, 102 Economy Plus seats, and 204 regular economy seats, for a total of 366 seats. Later on, when the Chicago-based carrier began installing its Premium Plus cabin throughout its widebody fleet, it cut out the first four rows of Economy Plus and replaced them with three rows of Premium Plus.