When you rate an app, leaving a comment is optional - and most people only bother to rate rather than also write a review.

For scammers to hide their tracks, they need to make sure they also leave a comment in some fraction of their submitted fake ratings. Apparently these scammers were too lazy, or too cheap (it costs more money to buy fake reviews, because coming up with the text requires extra effort). They just bought an insane number of positive ratings, and since the average displayed on the App Store is from all ratings & reviews, they can manipulate it to their liking using just fake ratings.

Most other scammers are more sophisticated and definitely include fake reviews to make things look more realistic.

I could be wrong, but I assumed it had the necessary number of (presumably fake) 5 star reviews that had no comments, and that the parent post was listing only those reviews that left comments.

Edit:

In other words, "reviews" below means "feedback with comments, excluding feedback without comments":

> look at the star breakdown of just the reviews - there's 835 of them