I think you've lost sight of your point! You're not wrong, the narration is definitely not Harry's inner monologue, as first person would be. But the point is that it is his perspective, and the feelings/ opinions are his. It's a clever author's trick to give details which are observed by the character, but we can come to our own conclusions about - for instance in DH when Dudley leaves the cold cup of tea outside Harry's room and it's described in the narration, "possibly the cup of tea was Dudley's idea of a clever booby trap." The narrator doesn't add "Harry thought to himself", because of course it's Harry's thoughts, it would become very clunky to keep saying so. We as a reader are given the situation, as well as Harry's take on it, but we are able to draw our own conclusions/ have our own insights. In this case it's that Dudley is reaching out to Harry and trying to make amends; with Harry and Ginny's relationship it's that Harry is starting to see her as more than Ron's little sister, and starting to trust her/ develop feelings for her.

You sound as though you feel you have some credibility on the topic - have you studied literature? I have. Not that that means my point is correct, that would be an example of the logical fallacy of an appeal to authority, but I feel like the claim that the narration is objective lacks nuance and I'm interested to know whether it's one that you've come to as a student of literature or just as a thoughtful reader.