amazon blackhat reviews

i am just wondering is this a blackhat technique or what's going on
oftentimes when I am reading reviews for a product, the reviews talk about a completely different product. for example, let's say I am reading the reviews for a perfume. most of the reviews are talking about car tires? how does this work? is this someone stealing someone's reviews?

You do this by using a file feed in the backend of seller central to merge individual ASIN's as variations under a parent listing.