Nev, I’m glad you pointed out about Leia, I’d thought that and wanted to emphasise it too, but then forgot. It’s a great reason for why she gave up her training.

And, as you say JJB, it also helps deal with one of the common issues people have with Luke in TLJ. It even explains his hesitance to train her, and his shock when she went “straight to the dark”.

As Nev says, it’s built on something inexplicit in the movies- but something intended by Lucas and one of those things that’s included in the novelisations and widely known to be canon, to the degree that it’s likely enough to reappear in new canon works too. Besides, why not reinforce it here too, giving the original idea the explicit references it deserves?

We don’t even need the chosen one prophecy here- Palpatine’s involvement in Anakin’s birth was not directly related to the chosen one thing anyway, it’s just that some Jedi thoight he was. I really like the idea that Palpatine had these really watertight plans, but that irony or the Force kept freeing his creations from their dark origin.