[pawpawdiv9]

i goggled it and it says:
This feature is optional on the seller side, but many sellers may not even be aware they have it turned on - eBay automatically opted all sellers in when they introduced it in 2021 and if a seller isn't aware of that, they may be losing sales and not know why.

also found this:
With the immediate payment option on eBay, a listing is still available until a buyer completes the purchase.
You can require immediate payment in both fixed price listings, as well as auction-style listings with a Buy It Now option. Here's how it works: Fixed price: When you require immediate payment in a fixed price listing, the first person who selects Buy It Now and completes checkout gets the item.