Are these new rear shackles "defective"?

Pretty much all of that stuff comes from the same place, Year One is a retailer not a manufacturer. So getting a “perfect set” from one retailer vs another probably has more to do with how long the stock was sitting on the shelf rather than it being an indication of a higher quality part. Been seeing that with the Moog parts recently, there was a change in production and the new stock doesn’t fit. But getting the older stock is a crapshoot, just depends on what’s on the shelf.
Well I guess I was lucky then !