He's right. I have recent first-hand experience of them deleting reviews of counterfeit products. The emails say:
"We investigated your concerns about product authenticity, and the information we have indicates that the product you received was authentic."
I've tried posting a review a further 4 times, each time only mentioning the quality issues and nothing about product authenticity. Every time, it's deleted within 24 hours, and I get the same email.
Amazon CS said: "As I further checked it here on my end, actually to tell you honestly, our partner seller is the one who manipulates the reviews on their product."
Who is the "partner seller" in this case? Amazon.com Services LLC.