NZ C is significantly different (worse) hard product on
their 767s going to Asia than the product they fly on
ultra-long haul to the US or UK via HKG.
The 30,000 miles may be worth it in this case.
TG doesn't usually sub planes with no F on those routes you've mentioned. It's shorthaul where they do that a lot. The plane they have on FRA-BKK right now (leased from 9W) is really nice in C and F (I've flown it in C and would cheerfully do it again- and on a BKK-FRA-SEA itinerary, for that matter).