I think it depends on the shipping method that is chosen.
If it's done through らくらくメルカリor ゆうゆうメルカリ then the name and address are anonymous. If you choose to send through the post office (or other method?) then the seller gets the postal details of the buyer.
This is done after payment is completed, so Mercari ensure they get their cut!
So in the example above the seller may have brought the goods to the house out of kindness or they may have been saving themselves the shipping fee. That would depend who was responsible for paying the shipping fee as either the seller or buyer can be responsible for that.