The Harvest Cycle is the birth year reduced to a single digit, which means it is not a personal figure at all. Everyone born in 1979 has the same Harvest Cycle. So does everyone born in 1988, and in 1997, because those years reduce to the same digit.
That is a different kind of claim from the rest of the chart, and it is worth separating out. The name positions and the day positions distinguish individuals. This one distinguishes cohorts, and any reading attached to it is a statement about a birth year rather than about a person. Roughly a ninth of everyone alive shares it.
Read charitably, that is not absurd. People born in the same year do share formative conditions, and generational description is a respectable if inexact activity. Read as the tradition usually presents it, as a stage of an individual life with its own character, it is doing something the input cannot support.
The reduction also collapses distinctions that a generational reading would want to keep. Nine years apart is a long time, and 1979 and 1988 were not alike; the system gives them the same figure because their digits happen to sum the same way.
Practitioners generally use the Harvest Cycle as the last of three life stages rather than as a description of a generation, which sidesteps the question by treating the figure as a timing marker. That works, and it means the shared value is doing less than it appears to.