As others have pointed out, the FDA is not slow-rolling review of Anavex 2-73 for AD because Anavex has not even submitted an application to the FDA for review for this indication.
Historically, indications with zero effective therapies often see additional extremely marginal-to-ineffective therapies approved (glatiramer acetate and beta interferons for MS, for example, or therapies for muscular distrophy, or recently a therapy for ALS.) It is not surprising that a couple of very, very marginal therapies were approved for AD.
When Anavex submits its NDA it will be in good shape to be approved.