Yeah and therefore, it's not the actual history because it only tracks the dates of when the people who have currently starred it have started starring it. It's a detail, but if someone unstars, it will be treated as if that person had never starred the project in the first place. Or in other terms, whatever graph is shown, you will never see it go down.
Edit: the code in question[2].
[1]: https://docs.github.com/en/rest/activity/starring#custom-med...
[2]: https://github.com/bytebase/star-history/blob/c8c66678db8015...