When you share something on Twitter, there is literally a script (executed by Twitter) that shares that same thing with all your followers. That's essentially the primary mechanism of Twitter, and I would argue that it's fundamentally very different than you choosing to call everyone to know to tell them something (at least for people with more than, say, Dunbar's number of followers). Because of the fact that it's automated, essentially instant, and essentially unbounded in its reach, it is mechanically much more similar to robocalling than to calling your friends to tell them something.