How it differs from product information
Product information is what is said about a product: capacity, weight, compatibility, price. Identity is what those statements are about. A correct capacity attached to the wrong variant is correct information and a wrong answer.
Why it breaks
A model assembles a product from several sources that do not agree on names: the maker's page, a retailer listing with last season's figure, a review of a bundle. Unless identifiers tie them together, the model resolves the disagreement by guessing, and the guess is invisible in the answer.
Example
"Trail 45" and "Trail 45 (2025)" may be one product or two. With a GTIN and the variant stated on each page, a model does not have to decide.