Maybe you are right. I do not pretend my English to be better than your.I'm not seeing it as free.
"The new scheme allows the seller to pay for an item to be sent over to the third party prior to auction. After receiving the product, the authenticator then performs a real life inspection, before sending the item to the buyer if all is in order. Additionally, a buyer can pay for an authenticator if the seller decides not to."
What it's saying is that if the seller has paid for the service, it's free to state it in the listing that the service is added and that the item will be re-reviewed before the buyer receives it.
"When the usage of the feature finally starts, sellers will be able to add it to inventories and listings of high-end fashion items such as handbags, for free."
and
For listings in the target inventory set where the seller hasn’t adopted the authentication service, the buyer will still have the ability to utilize the service for a fee.
I saw it as paid service for both sellers and buyers and only for same high-end items which exceed certain amount to be free for sellers. Same as on Poshmark Concierge where sales over $500 are authenticated for free. But eBay is greedy and may be all be paid.