UPDATE The practice was called "review reuse fraud" in this Buzzfeed article:
The mismatch between the product and the review may appear random, perhaps a glitch, but it’s a deliberate tactic Amazon sellers use to accumulate reviews. They take an existing product page, then update the photo and description to show an entirely different product. By retaining all the existing reviews, the new product looks more tested and legitimate to shoppers — and in the world of online reviews, quantity is key. More ratings make a product appear to be more well-reviewed and, ultimately, boosts sales.
A single page can be manipulated multiple times over the years. Based on the reviews for a hair-straightening brush sold by AsaVea, the listing was for an SPF 30 lotion in 2006, and then a deodorant in 2010, and then a St. Ives face scrub in 2012, and then a mascara in January 2018, before ultimately becoming a hair-styling tool.
Longtime Amazon customer Marat Nepomnyashy was scrolling through his Amazon purchase history earlier this year, when he noticed pictures of products he didn’t buy. He clicked on the product page, and was surprised to discover that an extended battery he bought in 2014 was now a ZeroLemon clip-on Bluetooth speaker. “I realized that the product sold has been switched, and my positive review was now promoting this new product that I had nothing to do with.”
After talking with Customer Support, I found out that the most direct way of reporting swapped product listings is to email cs-reply@amazon and mention the product's ASIN.