My understanding is that it can also exchange traffic peer-to-peer, either when two nodes find each other on the same wifi network, or ever over Bluetooth. So if a friend (who presumably follows many of the same folks you follow) comes to visit your off-grid hovel, they bring the most recent network state with them. Anything you've written gets merged with that state, and if they later go back to some other form of connectivity, it propagates that way too.
This gets really interesting if, say, you're out camping with a bunch of friends who are all on SSB. You take some photos of something you found on a hike, and post them. Your fellow campers can respond and interact, just like always, since the data propagates around the campsite. When (one or all of) you return to civilization, the whole corpus propagates to whoever else follows you, and they can see (and now participate in) the whole thing. Even if some of the folks are still off in the wilderness and their phones haven't seen a cell tower in months.
This gets really interesting if, say, you're out camping with a bunch of friends who are all on SSB. You take some photos of something you found on a hike, and post them. Your fellow campers can respond and interact, just like always, since the data propagates around the campsite. When (one or all of) you return to civilization, the whole corpus propagates to whoever else follows you, and they can see (and now participate in) the whole thing. Even if some of the folks are still off in the wilderness and their phones haven't seen a cell tower in months.