It's scratched
Likely because it's been refurbished. It's a genuine apple battery, you can tell by the serial # on it (3rd party batteries don't have this). But I doubt its a new battery, just new cells on the inside and clearing the micro controllers nvram (which is mostly all that really matters).
Never trust a battery that doesn't come from Apple
As an ACMT who's seen hundreds of third party batteries, I whole heartedly agree with this.
Buy a battery from apple
I'm not aware they allow this on the internal batteries due to the exposed cells and the liability of people setting themselves on fire. If they do, news to me. You can send it to them and pay to have it replaced. But I'm not aware of anyway they will legitimately send you one to replace on your own. And no, ifixit is definitely not buying straight from Apple.
Have fun when your battery explodes
You have a better chance of holding a winning lottery ticket while being struck by lightning. I've seen hundreds of Apple (oem and 3rd party) batteries expand. I've never seen one "explode" that didn't involve surge or massive physical damage.