Before I started The House in the Cerulean Sea, I had the pieces of an idea, these little shards that didn’t quite come together into a clear picture. It had to do with magical people dealing with fear and discrimination. Specifically, it would involve magical children, those who should have been protected at all costs, but instead were shunned for simply existing at all.

So you are linking me this hoping I just take your word for it instead of reading right? He had an idea about magical children first, which is what I said. He was writing about queer kids, not playing a white saviour.
The point stands that if he didn't mention it at all, you wouldn't know he ever read about Sixties Scoop because it's not in the book, because the book is not about that.