AGK allocate spending on the elderly to the elderly alone - as if their children who are freed from caring for them are not better off because of public health and pension programs. But they allocate spending on education to society as a whole, not the young. And they assume that present Medicare and Medicaid spending growth will continue - though of course it won't. Obviously, life as we know it would end before that could happen. If health inflation were to settle down to the general rate of inflation, the generational problem virtually disappears, even at high discount rates.
Sensible assumptions make the generational problem disappear.
Deconstructing AGK's devious arithmetic doesn't mean that the deficit isn't a problem. By playing games with time, GA completely obscures the fact that debts and interest payments occur between classes of people in the present. GA replaces class war with a spurious generational war.