Well that's the difference. If you are looking to sell it then there needs to be pictures with your name on a piece of paper. It's in the rules because people would like to see that you actually have the product and that it is in the condition that it is stated to be in. There has been people who say to have a product, post a picture off of photobucket or something and then collect the funds all while they really don't even have the product.
I'm not saying you are trying to do that but to avoid anyone doing that the rule was set in place. If you are genuine about trying to sell something it really only takes about 30 seconds to write your name on a sheet of paper with the date, snap a pic, and then upload it on here. If you go about it that way your post will not be deleted.