NFC can transmit arbitrary data, too (which is done on bt pairing, as the two devices exchage a bluetooth passkey).

As the data rate is (relatively) slow, there is no sense in transmittig big amounts of data (like directly sharing an image via nfc).

but as a keyboard has to send a minimal amount of data, nfc is fast enough. there is no standard for this though, there will be a special driver needed, which is polling nfc and emulates the keypresses for the os.