I would find it hard to recommend or see benefit in that drill, as demonstrated. Also, I'm hard-pressed to find enthusiasm for a drill that "really works the legs."
The significant deficit in the drill in the link above is that the swimmer is forced to brace and scull with the lead hand. If you're a believer in the importance of the quality of the circuits you imprint (and myelin or motor cortex neurons you grow), you'd never want to do anything that leads to bracing and sculling.
Likewise "really working the legs." My constant goal is to work my legs as little as possible -- even when working on maximizing the power output of my 2BK. I try to do that as much as possible with a well-timed weight shift and as little as possible with fatigue-prone and glycogen-gulping leg muscles.
When doing the BK drill Eric describes I work on maintaining even balance with impeccable weight distribution so my kick remains relaxed. And of course with well-tuned spinal stabilizers.