Haven't ebay reviews always meant to be about the seller and not necessarily the product? Ebay started with the expectation it was normal people auctioning used goods. Having reviews for a specific product doesn't make sense when there is no fixed product. Obviously things have changed over the years but the site is still largely built around those assumptions.

Yeah so when you view a listing now from a business it will show "100 units sold" but you're right it's crazy you can just change the whole product. I think it's specific for the business sellers.