The guide does not describe this fault directly. It asks for haul timing that suits the length of line carried and lists haul timing, length and symmetry as things to watch. From the mechanics it teaches, an early haul costs you twice.

• The speed lands too soon. A casting stroke ends when the loop forms, at the stop, and the line leaves with the speed it has then. A haul that starts before the stroke, or finishes before the stop, has already spent its pull: you do the work of hauling without the line speed.
• It puts the give-back into the stroke. In a double haul the line hand returns toward the rod hand during the pause; haul early and that return lands in the stroke instead, so part of the line is not moving and part of its mass is not bending the rod — the slack the Fourth Essential says to keep to an absolute minimum. The rod then bends less than the arc assumes, curving the fly leg upward into a wider loop; forcing it instead usually tails.

Practise starting and finishing the haul with the stroke: watch the hauling hand, and video it.

Source

From Task 15’s haul-timing, length and symmetry watch list in the CI Study Guide (2025) (PDF) and the Five Essentials it teaches — the answer itself is inferred, not quoted; terms from the FFI Fly Casting Definitions (Hauling, Casting Stroke).