On OEM bushings the center sleeve is not supposed to move, it's even bonded to it.
I think I think you've misunderstood the question I asked. Let me restate it to better explain where my head is at.
As the suspension compresses, the leaf spring flattens and "gets longer", causing the shackle to swing toward the rear bumper. This imparts some degree of rotational force onto the bushing and bolt in that eye of the spring. When the suspension droops, the spring "shortens" again and the shackle swings back toward the front of the vehicle
Unrelieved, this will cause the bushing to "wind up" like a torsion spring, which I assume is not an intended effect of cycling the suspension (in the same way that rotational stresses build up in a 231-equipped jeep operated in 4Hi on pavement where the wheels cannot slip).
Assuming that this "windup" effect is not part of the suspension design, there are only two ways that I can see to relieve it - either the bushing must rotate within the spring eye, or the bushing must rotate on the bolt.
Since the eyes in leaf packs do not normally come with grease fittings in them, I must therefore assume that the intention is for the bushing to be able to rotate freely on the bolt holding it to the shackle. The bolts we've been discussing in this thread support this conclusion, as they clearly are meant to supply lubrication to the space between the bolt and the inside of the sleeve.
With a urethane bushing, the sleeve looks (to my eye based on pictures) to have been made via extrusion - no seam, and perfectly cylindrical. Slipped onto a bolt in the hand, it seems like it should rotate quite freely. Not having handled any of this type, I don't know if the sleeves rotate in the urethane or not.
The sleeves in the OEM rubber bushings, based on the Clevites I used when I replaced my leaf packs several years ago, looked different. They appear to have been made by taking a flat piece of metal and bending it around a template - I could see where the two "sides" of that piece were brought together. When I slid a bolt into those bushings, I basically could not rotate the bushing at all on the bolt. This would explain why maxbraketorque reports delamination in his rubber bushings - the formed sleeves simply cannot rotate freely like the extruded ones found in urethane can.
My question was whether the binding of the bolt in the formed sleeves of OEM-style rubber bushings is supposed to occur, or if it's a sign of a manufacturing issue and they are supposed to spin freely as well.