From what you describe it is likely to be a new seller who does not understand the selling/bidding process.
What you have described is poor selling practice but neither the buyer nor eBay can force a seller to honour a sale.
The seller cannot cancel properly without the agreement of the buyer and will give themselves a defect on their account if they choose the wrong reason.
Too many of those and the seller’s selling days will be over for good.
The seller will also be charged FV fees based on the winning bid plus postage.
