The initial plan was indeed to have code zeros to use downwind in the light. However they have since shown that there are 2 major problems with this, one is that the drag of the sail once foiling was huge, and the other is that changing sail was far too costly in practice. So the only real use for them was, in theory, going to be in 6.5-7.65 ish knots of wind when foiling was not possible with the largest jib, and it needed to be cut in such a way to work upwind and down.
But once the wind was up, above that very narrow wind range and you could take off under your jib, you'd be a lot faster as you have less drag.
So you'd be making the call, at least 10 min out from the start of the race that the wind was going to be above the lower wind limit, but not enough to get you up on your foils with a jib.
And then they found that it wasn't actually any easier to get foiling with one anyway...
TNZ have tested one quite a bit, so maybe they'll bring it out in the cup, but I'd be surprised.