Just an update on this issue.

I never actually bothered writing, originally. Next time I went there, business as usual - no problems. In fact two weeks ago my partner, who has no status with star alliance, was warmly welcomed when presenting a SQ J boarding pass. No problems.

And then on Sunday, I struck the same person who I had my original problem with and I was advised would have been denied entry had she been at the door when I entered - but as she wasn't and I'd already sat down I was allowed to stay. 8 people were in the lounge!

So before I flew out I submitted a note online, and received a response this morning from the lounge performance manager, indicating that my interpretation was correct, and the matter would be addressed with the MEL lounge team to clarify the issue. Very happy to get such prompt feed back. Big ^^ to AirNZ in this instance.