Unfortunately, like explained in LMIC Library Always Does Unwanted Downlink - #12 by arjanvanb for AU915, you also won’t get channel configuration in the Join Accept in LoRaWAN 1.0.2 for US915:
2.2.4 US902-928 JoinAccept CFList
The US902-928 LoRaWAN does not support the use of the optional CFlist appended to the JoinAccept message. If the CFlist is not empty it is ignored by the end-device.