For whomever this is useful, my reading of the NB4 manual is that "2 way" mode is required for model-receiver binding, but happy to admit I have not tested it extensively:

From the manual:
[AFHDS3 1 Way]: It features lower latency, allowing one transmitter to connect multiple receivers. It is applied when the model does not need any return data.
[AFHDS3 2 Way]: With the two-way return function, it can return feedback data from receivers and sensors and realize one transmitter to one receiver.