Because it's a proof of concept using an ESP32, not because that battery capacity is fundamentally necessary for the idea to work. It could easily be optimized

Because it's a proof of concept using an ESP32, not because that battery capacity is fundamentally necessary for the idea to work. It could easily be optimized for power and size. Sure, it will have to use more power than a vanilla airtag, because it's doing (slightly) more, but not enough to make a significant difference.