After a while, once you've trained yourself, you can get rid of the guide and probably the vice too..
you are a carver, you know what sharp looks like.
I've never seen so many gizmos as I have since I've been on this forum. I didn't know all of these things existed. Thus, I learned to do without. I tried a couple of guides and a vice and stuff since I've been here. It felt like all of that just got in my way.
IMO, holding the bar solid with a vise is important to getting good consistent strokes with the file. If the bar is moving back and forth as you put pressure on the tooth with the file, keeping a good interface between file and tooth is made much more difficult. Consistency is key when it comes to sharpening.
I honestly don't see a down side to holding the bar still at all...especially with a stump vise considering how small and out of the way it is. Can it be done without? Absolutely, however it's way easier with.