Yes it makes it clear (but they can "commingle" the same product from different sellers, as said in the related comments).

However let's say you want to buy a product. But the reviews are mixed. Some are 5-star reviews, but there are 1-star reviews as well. And there are 5 sellers. From which one do you buy? All the reviews are mixed.

Perhaps a bad review is caused by a seller sending fake product. But perhaps the review is a valid review and it highlights a defect in the original product. You can't know.