That's shady. Normally, there's a bias such that people who are disgruntled are more likely to post a review than people who had a good experience. If you take that bias into account, a 4 star rating is pretty good, 5 stars is excellent, and so on.
But if you flip that bias on its head, 5 stars becomes a mediocre rating. That's ok if you've disclosed what you've done, but out of 165 reviews only one mentions that people are incentivzed to write reviews with free swag.
