If you remove the phone from the list of devices associated with your Apple ID, that will clear Activation Lock. The criminals will then be able to reset your phone to "make your phone their own", and have a like-new iPhone 15 Plus to sell to their customers.
Since the phone has turned up in China, there is a very good chance that it is headed for an infamous reprocessing facility that will chop it up for parts. Apple recently extended Activation Lock to iPhone parts, which eventually may help to put a dent in that "business."
Some people have reported getting threats sent from this place – when the initial "phishing" messages fail to work, the criminals proceed to sending messages with pictures of guns. If you get such messages, avoid engaging with the sender.