5G: In which scenarios, AMF initiates reroute NAS request procedure for a received Initial UE message ?

Question

I was comparing UE Context Release Cmd (defined in 36.413) with the NG-AP (38.413) UE Context Release Cmd. I couldn't realize the scenario in which only the AMF allocated UE NG-AP ID will be included in UE Cntxt Release Cmd. In LTE, both the S1-AP IDs were mandatory to send in UE Ctxt Rel Cmd from MME to eNodeB.
It would be helpful if someone can provide the reason.
Thanks in advance.

Answer 1

There could be multiple reasons to initiate this procedure for a newly received initial UE message at AMF. One reason which I can realized that due to change in network configuration such as mapping of network slices and associated AMFs, AMF can re-route the received initial UE message.
It is not necessary that change in the network slicing is the only reason to trigger this procedure because "Allowed NSSAI" is an optional IE in the REROUTE NAS REQUEST message.