The Silvans had their own ruler and were not taking orders from Linden. If they were going to introduce Silvan Elves into the show then they should have shown that they had their own king and ruler just as they did in all over versions of this story. Meaning, the only reason for this scenario is to create a situation of a small number of Elves get captured and nobody notices. Otherwise, if they were sent there to watch over the South Landers, then there should be lines of communications at the bare minimum, with the larger body of Elves being canonically close by in the Anduin realm on the other side of the Misty Mountains. Mordor is also on the same side of the Misty Mountains to the South East of the Anduin Having them under the command of Linden just makes it a larger distance to travel for information or news on the status of these soldiers which makes no sense. What is the point of having this outpost if they cannot get news of an attack back to the Elves in time for them to do something?