Had you reserved a battery and received confirmation that it was available? Or maybe miss
Need an iPhone battery replacement?
For iPhone 6 or later, Call or Chat with Apple Support today to reserve a battery before visiting an Apple Store.
The option was this or the original plan to have folks wait until the end of January before making the offer available so they could ramp up their supply chain. Making millions of batteries available in a matter of days just isn't realistic, IMHO.