I think sometimes writers tend to spend so much time working on something and it's all so clear to them that when other people don't immediately realise what we're saying it's like "..." With that bit in chapter 2 (to use your terminology) I realised what you were saying, and I thought about changing it, but the entire paragraph is prefaced with Over his years at Hogwarts, and to me, that is all inclusive. I wouldn't really call this timeline fiction as much as I would call it a story about hindsight.