To be clear, any battery updates are embedded in the AC firmware update. After an AC firmware update having a battery update is done, if the AC sees another battery out of date, it will call for an update to the battery. You can't update the battery directly.
It used to say "inconsistent firmware" but I believe DJI now has it differentiate battery update from inconsistencies with other components. I'm sure the generic freaked out many pilots.
The problem is that AC update process wants to be sure you have enough power to complete, lest the slim chance the battery runs out before the update is complete and the AC is bricked.