It must have been hyperbole on King's part to suggest that a fast "turnaround" would make a rep "near useless in terms of muscle fibre recuitment. We know from Newton's 1st law of motion (the law of inertia) that more force is required to change the direction of a moving object than is required to move a stationary object. So a fast "turnaround" requires more force to be produced than pausing the rep, and then restarting from a dead stop.
Yes, there is some utilization of the elastic properties of the connective tissues during a fast turnaround, but it's hardly enough to generate sufficient force to quickly change the direction of an 85% of 1RM load. Fast/ballistic muscle contractions (at least if the load is sufficient) recruit all available muscle fibers.