"black" is the same deal as their "zombiemax" ammo. its just a marketing shtick. it uses the same bullet, brass, powder and primer, loaded to the same PSI spec as any standard version of their ammo of the same bullet type/weight/caliber.
now, there's going to be lot to lot variance like there is in any ammo, but otherwise there's no difference.
i suspect someone was trying to move old inventory off their shelves, especailly if he had "pallets" of the stuff in stock.
if there was a legit issue with hornady black coming apart in flight, they would have requested the ammo back from whoever experienced the problems and have already been testing it to make sure they dont have to issue a recall. from my experience, hornady takes the safety and quality of their products VERY seriously. if there was an issue, they'd let us know ASAP.
I had some zmax ammo (about 200 rounds) a few years ago in 308. having some pressure signs showing up in my 16" LR308 (ejector and extractor swipes, cratering, etc) and when i contacted hornady about it they immediately had me return EVERY box i had for testing and evaluation. It was fired in a pressure test barrel, and found to be within spec. They replaced it with Hornady Custom - the exact ammo in a tan and red box - because they didnt have zmax in stock and i didnt care if it had a green tip or a red one. Come to find out - in my instance - that all the ammo was well within their load specs, and my gun was just over gassed badly because its a carbine gas 308.
you can find all recall information for hornady ammo on their website if needs be
https://www.hornady.com/support/product-recalls/