We should not be surprised that FIFA are staying out of it. Them stepping in undermines OFC (like they need any help with that) It's like running to Dad when Mum says no. FIFA have confederations to sort this stuff for them regardless of the incompetence.
So effectively, what the keyboard detectives have discovered is true in that if you have a passport and no lineage, then you can't represent your new country until you are 23 - the kicker is that it's on the new countries FA to apply for an exemptions do showing just cause for it to be applied.
If I were NZF, I would be doing up a spread sheet with columns and checking off each players name in the u17s, 20s, 23s and AWs and any potentials. Now that this is fully exposed in the spot light, you can bet other FAs will come looking again in the future and we need to go back over every single player and ask the questions.