The GPS locators are heavier with shorter battery life. This has been my experience from GPS pet trackers. Since Bluetooth Low Energy does not require as much energy or range, the form factor is greatly decreased.
The Nordic Semiconductor NRF52832 used in the airtag, unlike NRF52840, does not support this.
https://colinoflynn.com/2021/05/apple-airtag-teardown-test-p...
https://www.nordicsemi.com/Products/Low-power-short-range-wi...
Apple seems to have removed support for long range coded PHY from iOS as well, so other vendors can't make use of coded PHY either. It was present in iOS 13, seems to be absent from iOS 14.