Hi
Moko IS a hatchling. That is why the best time to introduce another is now, IMO.
Of course, you are correct that there are NO guarantees that they will get along for sure, or for now and for always. They change throughout their lives, and may not get along, or get along again at various times. This is why it is recommended to have a spare cage handy for those times. My male/female pair could use some time apart right now. The male has turned into a pest. I don't think it will always be like this, this is just right now. They normally get along well.
Being the same sex is not a cause for fighting, it is more often because they did not grow up together. This is what I have read, of course, from the experienced guys.
You people with savs really need to start breeding them. The wild population can't supply the hobby forever.
Cheers. D.