Trusted means that it is approved to sell in the forum and there is a feedback section which is the voice of the customers. You know what you will receive, not just a random website you found on google with AAA+ replicas.
A dealer is a team. There is a lot of work with website developement, qc pictures, emailing, several type of shady payment handling receving money and paying factories, illegal pp accounts, third party credit card payments, watch orders, relationship with factories, package making, aftersales service etc etc
The qc picture is mainly for the reason to make sure you receive the watch you really ordered, and not a different one. However if you see something unusual, like scratch on the dial or some kind of misalignement you can ask the dealer to take you some more pictures. This is the benefit of a forum, and a ¨trusted¨ dealer.