Apple 100%. The "Battery replacement" is essentially a swap for a remanufactured iPad, which is new enclosure - new display - new battery. The only thing that's "Refurbished" is the circuitry inside.
The only "issue" with Apple replacement is that the battery has to be below 80% of original value, on their test. If you're not sure, chat/call AppleCare and they can run a remote diagnostic to see.