Interesting. Android has a Nearby Connections API[0] which "uses a combination of Bluetooth, BLE, and Wi-Fi technologies" and appears to allow interoperability between Android and Apple devices, and Apple has a Nearby Interaction[1] which "use[s] the high-frequency capabilities of the UWB chip" but is restricted to Apple devices, so I guess it could be one of those rather than NFC.

[0] https://developers.google.com/nearby/connections/overview

[1] https://developer.apple.com/documentation/nearbyinteraction