And to carry this a bit further - I'm quite familiar with the Class system of hiking/climbing used extensively in the West. Once familar with it, most hikes/climbs clearly fall into a specific class (I thru V) without much disagreement. Class I is on trail, using only your feet. Class II may include offtrail, and occasionally 4 points of contact (you'll need to use your hands). Class I and Class II are hiking. Class III begins the climbing. Once Class III is reached, it's clear that a fall may result in injury, but probably not death. Class IV means that a fall will result in certain injury, and possible death.
So - when the author Phil Brown uses the term "fourth-class climbs" - does he mean Class IV in the system used extensively in the West and elsewhere, or is there yet another classification system he's referring to?