@StrikerEZ The simple answer would be that the fabrial has multiple spren gems inserted in it, so you can point to any of them. That Jasnah fabrial always comes to my mind with 3 or more gems in it? Also we spoke with @Calderis on discord about ancient fabrials. He believes they used a more sophisticated way of communicating or maybe they are powered by a different type of spren. In any case I believe the role of the spren is to communicate, what the fabrial user wants to do. Stormlight might be used as an enhancer, like a megaphone, so your example can reach more spren once at a time. It can also be used as a torture tool. Like you show the free spren you want to modify, your captured one and to make them comply, you start electrocuting the prisoned spren with stormlight. This sounds really bad, but take a horse for instance. You whip it, in other words you inflict pain on it, so it starts doing what you want.
Imagine if I'm right, Navani would be the master torturer , thinking of new ways to torture the poor spren,