A well-known Twitter leaker claims to have found a new Korean safety approval for a battery that may go to an Apple device with the model number A2431. Therefore, it may pertain to an iPhone 12 variant. If so, it may be much smaller than those of the 11 series.
https://www.notebookcheck.net/A-new-iPhone-battery-with-a-sub-3000mAh-capacity-is-reportedly-certified.482789.0.html