Earlier quoted context omitted.
The concept of peak oil is fine (almost self-evident), just the timing has been off. Theories are easier than predictions.
Although Peak Oil won't really happen if demand drops before we hit the supply peak. We might transition to renewables and eventually fusion and never actually experience the specific dynamic Peak Oil envisioned.
I think he was implying that the transition to shale is an indication that we are moving to unconventional sources, thus indicating we've peaked on traditional sources.