Johnny, I dont have a clue why the stock pulley would squeek...

My guesses are....

Someone posted on here that his rivets came loose, or just got old, and so his backing plate moved around and touched the clutch at times. Its possible if rivets are loose enough then the whole backing plate could get angled, like my code 3, and cause a squeek on engagement.

Or, a person's belt could be worn, or belt tensioner is broke. Same effect. If a belt is loose then the clutch engaging the s/c pulley would be able to slow the pulley a little because the belt is loose and not snuggly holding the s/c's spin against the clutch's engagement, causing a quick squeek.

I dunno... It could as simple as dirt in the wrong place. Or a small rock. More likely than you'd think!

Or, someone's s/c clutch's face wore down a little and can now squeek when it first contacts the pulley. That's always possible.