I now have an update:
- NSC started by CO October 2017 (not when ITA lodged in Dec 2016)
- Feb. 2018 I sent an email asking for update
- Next business day, INZ said NSC was "clarified" -- decision reached by CO and pushed to 2PC
- Three weeks later, 2PC confirms NSC is required
- NSC "restarted" -- they said no need to go to back of queue, so wait is for NZ office, as foreign countries don't really care about changes in NZ processing status
- In April 2018 NSC will be eligible for expedite as it will have been 6 months
This info seems also to indicate that NSC is mostly an NZ-based check, rather than waiting on a response from a foreign country. This would mean NZ's security check is more in line with what most countries do -- standard criminal database checks/histories, with inquires with foreign authorities only in special cases. (It's unusual to allow standard security checks to sit on the desks of foreign ministers for 6 months, and then suddenly have a response.)