Watch as I straddle the fence here ...
Recurrent shoulder instability is tricky. One of the laws of orthopaedic surgery is that the best chance at a great result is the first chance. Having required a second procedure isn't ideal, and usually indicates a worse instability.That said, there are revision operations that can be very successful.
It's possible that they just want to be extra protective - no one wants a third surgery for this. It's also possible that there are some concerns about the stability, and the shoulder needs more constraint. Without knowing more about the original surgery, the second procedure and the anatomic problems they were dealing with I can't tell you more.
My advice: be cautiously optimistic . How's that for fence straddling?