Do you have the standard capacity pack shipped with your P4?
I do not OWN a P4. I have a P4P. It ships with the NEW battery. The battery in question is the standard P4 battery that also works in the P4P. They are different batteries. That is why there is a price difference.
(I haven't seen it claimed as genuine DJI OEM anywhere).
And, there is your caveat once again. A subtle clue that you still think the seller is not selling a genuine DJI product.
In fact, the seller of the battery DID state that it was a genuine DJI battery, but it was not in the King's English... so I guess that means he is up to something...