From what I had read it was sought of agreed on a global standard but not signed on that Bluetooth would be the medium of choice for NFC...

However, since it wasn't a signed standard, Google chose to use the WiFi antenna of devices to do the transfers instead...

Its a similar situation to Apple's headphones standards which mean many new/popular headphones don't work on the N9 without an adaptor due to the way the contacts are wired...Nokia used the global/prevalent standard, Apple re-invented the wheel and got away with it due to their size same as Google & NFC...