I'd never heard of "drag catastrophe" before either, but I think you're right that he's referring to the onset of turbulent flow that reduces drag on a bluff body.

That's the sudden drop at the right in all of these graphs: www.google.ro/search?q=drag+reynolds+number (same as his own Figure 9, really).

There are a lot of surprising nonlinearities in those graphs. I wish there was a more detailed article/paper somewhere.