NWK_addr_req response for sleepy end devices

From the specifications,

    NWK_addr_req can be sent unicast or multicast.
    IEEE_addr_req can be sent unicast only.

For sleepy devices, zdpMsgProcs[] in ZDProfile.c setups up a response to IEEE_addr_req, but not for NWK_addr_req.  Are we assuming that the parent always responds to NWK_addr_req on behalf of the sleepy child, that the child never haves to respond to such request?  Shouldn't a sleepy device also correctly respond to NWK_addr_req the same way it responds to an IEEE_addr_req?

This is with ZStack 2.5.0, but I see the same behaviour in ZStack 2.5.1.

Thanks.