With respect, what does this jig provide you that you can;t achieve with setting the fence and cutting?
A properly tuned and adjusted saw should be able to repeatedly cut uniform boards without issue. Using an accessory carriage type of system seems redundant.
What am I missing?
I don't think you're missing anything. It's more that it is an alternative approach to resawing.
I'm happy with the setup of the bandsaw and I like to think that it is properly tuned and adjusted although I'm no expert in that area so it could possibly be improved.
The fence that comes with the saw is low level and won't work for resawing. Before I made this jig I used an addition to make a single point fence for resawing which worked well enough but meant that there were more operational parameters that I would need to address during the cut, namely holding the timber against the fence for vertical alignment and maintaining alignment with the blade as I pushed the piece through the cut.
I considered making a tall fence and an associated feather board assembly as an alternative which would have been fine. And in effect, that is what I've achieved but in a different way. Attaching the timber to the sliding carriage is the equivalent of a tall feather board and the height of the fence is built-in.
(In my head it's similar to the difference between a table saw with an extension table and a long mitre fence and a table saw with a sliding carriage - same cross cut capability but the timber can be more securely held on the sliding carriage).
The obvious problem with my jig is the length of the board that I can resaw. I still have the single point fence if needed but in the main I work on smaller items.
For me the best part of using this jig is that I only have to concentrate on the speed that I feed the timber through the cut. And I'm still convinced that getting the speed right is as important as the tuning of the saw.
I guess the short answer is that this is not
the solution but one that works well for me