Looks like this issue has been pretty well resolved without me having to say anything. However, as I can't help meself, I'll just say that, in my dark little corner of the planet, we also refer to DA, MDA and RH. We agonised over the "RH" but decided to leave it there in case we ever adopt Cat 2 approaches.
I really don't see that happening here, but at least you now know the rationale. I'm guessing it's the same rationale in Oz. Ooops... I know... mustn't guess...
I was just fractionally troubled by this comment by
Aotw though...
We used to set it at the appropriate obstacle clearance height on a non-precision approach, again as a guide, ie 400 ft for Cat B.
I trust that you only set this for circling. OCH in the final segment of a straight-in NPA can be as little as 250 feet.