Hello Mike,
as Neill explained, we changed the way to implement these links handlers to make it easier for developers. You should implement it like it's done in feedback.
Neill is right about the ":index" too, it's to make sure the name is unique. This name is only used to identify the handler, it isn't used for anything else. With the old implementation of links handler, the modules had a single handler to treat all the possible links of your module. With the new implementation, the addons will have a link handler for each type of link, that's why we add those prefixes to make each name unique.
Kind regards,
Dani