Snagly, I read that same passage which lead to an additional 15 minutes of pondering while on the shitter. He could've also been referring to the classic "thump-thump" steelhead bite while drift fishing. These two bumps felt in rapid succession elicits a quick hookset on my part.

But, more likely he's giving us advice he probably gives all his clients. WAIT for the second, third, even fourth takedown, until that rod is buried, before setting. Works for most techniques, especially with good bait.