NS-RESET / NS-UNBLOCK / NS-BLOCK are not specified over IP/UDP
According to (at least) Release 6 of TS 48.016, the NS-RESET, NS-UNBLOCK and NS-BLOCK procedures are not to be used over an IP bearer, i.e. they are only for Frame Relay.
Historically, we implemented our Gb implementation for OsmoSGSN in order to interoperate with nanoBTSs. So ip.access appears to have been in violation of above spec, or earlier releases of TS 48.016 still allow or even require those procedures even over IP.
So if we want our implementations (OsmoPCU, osmo-gbproxy, OsmoSGSN) to interoperate with 3GPP (at least Rel6+) compliant other implementations, we need to be able to disable those procedures basd on configuration. This way, we can disable it as needed.
Interestingly, our implementation (using RESET/UNBLOCK) works e.g. with the Quortus SGSN ;). On the Other Hand, some modern Ericsson SGSN/S-GW apparently outright rejects the NS-RESET sent by libosmogb.