Someone correct me if I am wrong, but the way I remember it, mature content is hidden by default and you have to unhide it when searching for content in the search options, but you don't have an option to make mature content visible in individual contributors' ports, just on the overall search page.
It's one of many mistakes on Shutterstock they either don't care to fix or are not aware off, since there is no communication possible between ocntributors and Shutterstock staff.