Johnny, the renntech is not a s/c pulley, so this wouldn't happen to you.

Heres my theory... The pulley backing plate has to flex its connectors, whatever they're called, when the clutch magnetizes and pulls the pulley's plate towards it. Simple.

If you have your pulley spaced too far away from the clutch, then the backing plate has to flex further to reach the magnetized clutch, and obviously the further it flexes then the more resistence it receives from its mounting point. Which means it touches the clutch with less force since the pulley is pulling it back. This loss of pressure can cause a squeek when the backing plate and clutch connect because there just isn't enough initial pressure so a slit second of squeeking friction occurs.

Therefore you remove a spacer which moves the pulley closer to the clutch and now the pulley backing plate travels a shorter distance to the clutch, receives less resistance from the pulley, and presses against the clutch harder, so no squeek on initial impact.

Of course I won't know this for sure until tomorrow morning when I start the car from cold....