That example is spot on and I won't pretend the tool solves it — it can see the field name changed, not that item_price can be zero.
Honestly it's made me think the more useful thing is a pre-commit prompt: "this change looks non-obvious, add a comment?" rather than a post-push summary. Different problem entirely.
Fair point — the "why" lives in the developer's head and no diff reader can recover it.
The bet is that automating the "what" frees up your commit message to carry the "why" instead. Most messages today are wasted describing what changed because that felt easier to type.
The pre-commit nudge you're describing is the better product though.
That works great if you're the only person on the codebase.
In practice, one person on your team uses Claude, one uses Copilot, two use neither. Commit Changelogs makes readable changelogs a property of the repo, not of whoever happened to be in the mood to prompt an LLM that day.
Also — it reads the actual diff, not just your commit message. "fix stuff" becomes a proper entry describing what actually changed. That's the part no one bothers to do manually.