In Apple Podcasts, ratings and reviews are not the same. You can leave a star-rating without writing a review, but every written review must include a star-rating.
If you look at the reviews tab for your podcast in the Apple Podcasts app, you'll see two separate numbers: a number of ratings and a separate number of reviews. It's common to see more ratings than reviews. That means some of the people who left a star rating did not include a written review with it.
Podgagement tracks both, but lets you see the spread of ratings and the difference between your ratings and reviews.