I honestly fail to understand where the advantage of a blockchain is here? Who adds anything to the blockchain? Is it only authorized sellers or employees of t

I honestly fail to understand where the advantage of a blockchain is here? Who adds anything to the blockchain? Is it only authorized sellers or employees of the luxury goods? If so, how is that better than just a central database. Also how do I prove that I'm the rightful owner of one of the luxury products? Specifics matter in these kind of use cases.