Well the fact that forged is known to slap must mean its an acceptable phenomenon and subject to a range of factors such as materials, piston design, clearance, ambient temperature etc.
Some here have claimed that GM have deliberately cut on quality control and although I can admit that GM quality is nowhere near as good as some other brands, I find it hard to believe they would have cut QC on this specific matter. Surely they would weigh up cost vs risk and consider the experience they had with earlier LS1 engines. Why would they foolishly expose themselves to litigation and a forced recall to repair all LS3 and other variants that are displaying a fault. It would cost them their reputation not to mention the significant financial burden to rectify the issues with a rebuild. Also the impact on their service network would be huge.
If QC was an issue for GM, they wouldn't be building engines in Mexico...
LS3 quality has been an issue before.
HSV imported a bad batch 2010/11, they had soft cams, and were losing lobes in less than 5000kms.
Holden's LS3's were the last to be mass manufactured for OEM fitment.
They probably used up all the miss matched bits and pieces to clear inventory...
After all, it was being shipped half way around the world, to a place, and country, that GM management was about to dump.