Do these stand alone south america legs have to be direct connections from your intercontinental flights?
The ANA tool naturally gives availability on JJ at the T-6 month mark provided you're searching (for example) a straight through same day connection from IST-GRU-EZE.
If you're planning to break the journey in GRU for >24 hours (and therefore searching for the GRU-EZE leg separately) , it won't show till T-3 months.
That bit about NH tool availability I understand, but in practise are the stopovers bookable at T-6?