Mollison's Permaculture Zones - what happened to Zone 5?

I've noticed a little drift in permaculture zones, away from Mollison's original conception, a trend toward moving the zones of human influence outward until there is no zone in which human use is not the primary function, that is, turning Zone 5 into Zone 4, and thereby eliminating Zone 5.

Mollison describes Zone 5 in this way: "We characterise this zone as the natural, unmanaged environment used for occasional foraging, recreation, or just let be. This is where we learn the rules that we try to apply elsewhere."