Many members open accounts do not use them for years, and then perhaps wish to buy that one item and use the dormant account again.
Has eBay sent you a message that the buyer has paid? Then, with the correct insurance and tracking post only to the name and address shown on the delivery details, provided by eBay.
It's always a risk selling an iPhone as they are scam magnets, but it's also a risk selling to someone with a high feedback score.
It's truly up to you if you wish to proceed or cancel the sale, as there's no knowing if this or any other potential buyer is genuine.
Many years ago I sold my daughter's iPhone, but I listed it as collection only and it was cash on collection after purchase , so there was no comeback, no case could be opened for a return, but this has all changed now that cash is not allowed now.
@crafty6272