One can depart, fly 2 miles from the field, hold for six hours, and continue on one's way, to a point 50 miles away and land. Cross country complete. Perhaps 6.5 or 7.0 hours of logged time, 50 mile distance. It's cross country time and meets the regulatory definition.

The hours don't have to add up.

I've had flights that were over four hours and the total distance was about fifteen ground miles. Between the very long taxi departing JFK, the vector quite some distance away to get into the congo line to get into Newark, the approach, landing, and taxi in, it took four hours to knock out a few miles of trip. I don't log cross country, but while not 50 miles away, it would have been cross country for certain purposes, with a landing at a point other than the point of departure, as well as a flight to a point at least 50 miles away. It would not have been cross country for the purposes of a private or commercial pilot.

The definition of cross country changes with the application, and there is no requirement that one fly straight point to point. The flight time, in accordance with the regulation (and numerous Chief Legal Counsel interpretations thereof) commences when the aircraft moves with the intention of flight and ends when it comes to rest after the flight. There is no definition provided by the FAA or the regulation itself which suggests that the cross country time doesn't include the taxi at the beginning and end of the flight as well. It's a cross country flight, and insofar as the calculation of the flight itself goes for logging cross country time, the standard definition is the correct one. The flight time for the cross country flight has a beginning at taxi and and end after landing with taxi, which may be included as part of that cross country logged time.

They do have to add up when it's the other way around, i.e. flying a Skyhawk that cruises at 180kts both ways in still air. The examiners started applying the 0.2 as a sniff test of sorts. Which seems to have been taken to somewhat of an extreme over the years, perhaps due to new instructors and examiners not understanding why this methodology was implemented to begin with.

I used to help my students out by incorporating slow flight, s-turns, chandelles, lazy eights, etc enroute (if they weren't having any issues navigating). I would turn a 50 nm flight into a 2-hour adventure. Considering that they would have to determine their position again after each maneuvering event, I am pretty sure they deserved to log all of that time as cross country.

Well, they paid for it, so they sure as hell deserved to log it ;)