did you reoptimize FSRS on day 28 (or manually reschedule a large number of cards)?
I think the existence of RevlogReviewKind::Rescheduled is relatively new, so I wouldn’t be surprised based on your post to learn that a previous version of Anki was doing something like logging the FSRS rescheduling using a different review kind, but I’m only familiar with v25.02 logic.
If you’re really curious there is a Python package that will pull the data used in these reports into Python dataset(s).
You can also probably figure it out by clicking on the bar of the histogram with 3000 reviews, that takes you to the browser, and then right-click on one of the cards to get Info ...