Trigger Delay with Circle Path
 

From 10-14-A Standard Hip Turn:

Could anyone please elaborate on this?

HK is more or less Telling you what is happening rather than outlining a prescription for this procedure.

Normally, Circle Path Delivery is a Non-Pivot Procedure (Arms and Hands Only). But, in a broader sense, Circle Path Delivery refers to any Stroke that does not include a Straight Line Delivery Path before the Pulley (Release).

In this Broader sense, without a Straight Line Delivery Path, Hand Acceleration does not exit, which would create an Automatic Release when Hand/Elbow Acceleration drives the Right Forearm, so the Acceleration sequence is Right Shoulder-Clubhead rather than Right Shoulder-Hand-Clubhead.

With a Straight Line Delivery Path, the Pulley phase begins at the end of the Right Forearm Drive, which is Clubhead Acceleration. But, in Circle Path, of this kind, the Right Elbow moves with the Pivot and the Pulley will not begin until the Pivot Subsides or the Pivot can Throw the Hands.

This is an Elbow Plane Procedure, so a Standard Pivot helps and coordinates Plane Shift and Hip Action for Release (The classic "Sit-down" Pivot). Hip Action will "Throw" the Hands into Release. Very common among better Players.

Why does HK say "but only with a Delayed Pivot"?

Because he's giving and example of an Elbow Plane Swinger. Pivot leads/Powers the Downstroke.

If it were a basic Circle Path example, the Pivot would be static.

So this would not apply to someone using TSP with Zero Plane Shift?

No, not at all.