I was thinking that perhaps this lot didn't fully expand the way there were designed? Perhaps it's more likely to maintain it's shape?
I should think this is the least likely explanation. A while back there was a surge of Speer Gold Dot .40 ammunition that was being sold in bulk for near the price of FMJ ammo. It was specified for non-LE (actually, target) use, as is your Federal ammo. In Speer's case, this was because, as the last poster speculated,
It failed QC some way--maybe or maybe not serious. You'd best consider it plinking fodder.
The Gold Dots had a 1 in 10,000 chance of misfire--no where near acceptable for carry ammo, so Speer had to bite its lip and just about give it away.
I'll bet that if you called Federal and gave them the lot number off one of the boxes, they would tell you something very similar.
But, actually, it is strange that Federal merely said no Law Enforcement use, not "Don't
anyone , civilian or LE, depend on this ammunition for carry". If there were a critical reliability problem, I have to imagine they wouldn't want a citizen carrier to suffer for it either, so maybe I'm off base here and something else is going on.