They're in the same boat as UPS and other cargo carriers. So, when we can work around the problem of not having a secure cockpit door between us and the jumpseaters/pax then offline jumpseating will resume. This is really a question you should be asking the FAA, not the individual airline. They have mandated the same aircraft security procedures as the pax carriers. Unfortunately, just behind the cockpit is the cargo area. Jumpseats are in the cockpit and there is nowhere else for them to sit. Until the cargo carriers can get the Feds to relax their security ruling we're stuck with no offline jumpseaters.
When will that happen? Who knows but hopefully soon!