From a neo-apostolic perspective, the link from the NT apostles to the current "apostles" is not one of traceable historical line (as in the classical, Catholic or Eastern versions of "apostolic succession" which confers to the successors apostolic authority but not necessarily the title and status of apostles). The new "apostles" are validated otherwise, usually by cooptation in practice, but theoretically because they fit the qualifications and role within the community. Self-validation for the institution and then validation of individuals by the institution.
The WT "history" as presented to and believed by JWs (starting with Russell restoring "scriptural truth" against Christendom on doctrinal issues like Trinity and hellfire, iow negative doctrine, and 'foretelling 1914') works as a miraculous or providential "sign" which validates the WT globally in the eyes of the adepts.
I think donuthole aptly sums up the current practical although unofficial JW belief: to the average JW, FDS = GB = WT = modern-day apostles. The WT current writing line doesn't make this equation official (and maybe never will) but comforts it in practice.