To me, this doesn't make any sense.
This is why I don't buy into this particular part of the story. The story *does* have a lot going for it, and for me the positives outweigh the negatives.
He does provide "also" training by a third party, namely Mandisa, but it is true that he does most of the training himself.
That said...
The library is written from the point of view of Zaton, so on occasion it is less than factual and more an interpretation.
Those notes are his reasonings and motivations.
Much like any parent who is focused on pushing their offspring to their limits (think of the parents of star athletes who competed from an early age), his reasonings may be flawed, his methods may have unintended consequences.
As a matter of fact, Zahra actually sort of calls him out on his choice, albeit not explicitly.
Shani herself does so too, on the eve of her departure... and he concedes the point