The main difference between the iPhone 13 and the iPhone 12 is that the iPhone 13 will support faster charging and reverse charging.
The change could be explained in one of two ways. The most obvious advantage is that iPhone 13 would control heat better with a larger coil, allowing for more power.
Alternatively, the larger coil may be required to enable reverse wireless charging, which Android rivals have been delivering for some time.
Stronger magnets for the MagSafe are another recent rumor, and it appears to coincide with the more significant coil claim. The camera configurations may be the same as the previous model, but the phone would be larger than the iPhone 12 range overall size.