For the records, PROC_RPC is listed as RPC type process, but it's actually used for generic non-sip-worker processes that need to send sip traffic or access the resources that are enabled in child_init() by the other modules.
By using PROC_RPC does not mean the process will listen automatically for rpc commands and do only that.
Anyhow, if using PROC_NOCHLDINIT works as expected, then its ok to use it.