Not so. The specific tactic the NYC recommends is questionable, but it is possible to surrender your boarding pass for the onward flight. (Say you no longer want to fly: there's nothing they can do to stop you).

Note this is also possible if you check luggage: the airline is not obligated to let you get the luggage off the onward flight, but there's no airline that wants to carry baggage for a passenger who's not on the flight anymore (for security reasons).

If you're planning such a stunt (with baggage), try to have around 3 hours hop-time; else you WILL be delaying the onward flight with your luggage.

Layovers > 4 hours are considered as off-the-airport stopovers (domestically, US). That means the fare you'll get for SFO->DFW->BOS = SFO->DFW + DFW->BOS (made up routing). Exceptions: DEN for UA, ORD for AA, SEA and ORD for AS etc ("transit hubs", that is); where stopovers are free.