Is Amazon’s Handling of James Comey’s Book Reviews Unfair to Other Political Authors?

At the time of this writing, James Comey’s book, A Higher Loyalty, had received 740 product reviews on 94% of those reviews are positive (4 or 5 stars), which is well above Channel Signal’s across-industry average of 84%. With such a super-charged political author, it’s surprising the reviews aren’t more polarized.
Upon investigation, it looks like Amazon has decided to restrict reviews of this book to “verified purchasers only.”

Amazon restricts the ability to review some products if they detect unusual review behavior.

Gating reviews with the verified purchaser limitation can prevent biased reviews from users who have not actually experienced (or in this case, read) the product. In this case, the probable goal of the requirement is to censor out inflammatory negative reviews.
Yet this is not something we see often from Amazon. Although a user always has the ability to filter reviews by verified purchasers, it’s rare that Amazon implements the restriction when writing reviews. According to Deadspin, they put similar restrictions on Hillary Clinton’s What Happened and Michael Wolff’s Fire and Fury.

The Contrast

In contrast, take Megyn Kelly’s book Settle for More, which has a mere 75% positive rating. Channel Signal wrote about this among other products that seemed to be victim of review trolls. There is no verified purchaser gating on this product, which seems to have plenty of trolls.

Some reviews do not require a verified purchase.

Similarly, Ivanka Trump’s Women who Work has no verified purchaser limit on reviews.
Amazon’s specific criteria for what is considered unusual activity is not publicly known. What has been public is their efforts to reduce fake reviews, particularly those that are a result of promotional product exchanges.
It seems that this type of review gating for any controversial product could be implemented to prevent bias. If Amazon intends to share the true voice of the users, why not apply verified purchaser gating to reviews of all controversial products?