As I recall, they had a larger "chase" boat following them for their catboat voyage (or did just the son sail the catboat, with dad in the chase boat?). So, they were a bit more prepared, by design, than you intimate.
And, Vertues are pretty well respected bluewater boats. In fact, for their size, I can't think of any designs with a better offshore reputation. (But, I still can't imagine being trapped on one with my dad for weeks on end. Sooner or later, one of us would be bound to break.)
In any case, sailing is as much (or more) about the sailor as it is about the boat. Remember, Capt. Bligh and his remaining crew sailed an open (and engineless) boat 3600 nm after the rest of the crew of Bounty mutinied. Granted, that was back when boats were man of wood, wrot iron, and tar, and men learned their sailing skills on the open ocean, rather than via books and the Internet; so we can't quite compare Bligh to someone in a fiberglass boat, with an aluminum mast, dacron sails, stainless steel rigging, an auto pilot, and several thousand dollars worth of navigational do-dads. And of course, Bligh never benefited from reading all the opinions of arm-chair sailors on SailNet. But, still.....
I think also of Shackleton and crew in the lifeboat JAMES CAIRD. Shorter mileage than some sagas, but an awful climate and get-that-noon-sight right-or-we-miss-the-island-and-all-die was quite true for them.
I read, and really enjoyed, the Hayes' book.
This particular quest, however does strike me as kind of holier-than-thou, as others have suggested. Occasionally with sailing students and the right breeze, we'll sail into the harbor and into the slip to the tune of the "Motor? We don't need no steeeenkin' MOTOR" chant, but we all know it's nice to be able to crank it up when our "engineless" pranks don't work out so well.