Are we discounting or forgetting the destabilizing effects of the plateau itself?  And how those instabilities in complex systems such as financial markets and geo-political relations will affect oil production.  For instance, the extreme instability manifested in Iraq right now could easily lead to sabotage in the oil fields.  If Iraqi oil goes offline this coming year, oil will (at least) spike up to the $80-100 range.
I think Khebab is using just the geology to define the upper bounds of the supply, which establishes why this may actually be the peak plateau and not another interlude. The effects that emanate out from that are not as amenable to pure statistical analysis. As you note, they have the potential to be massively disruptive also but one cannot make specific predictions about how the overall system will oscillate out of control. Instead Khebab is trying to show that we're at the point where this oscillation can occur. At least that is my understanding here.