The custom splints and custom pieces eg the down graft material shape from the VSP are much more important than the custom plates.
The VSP read out tells the surgeon what the displacements are. Although they might be listed with small fractions of 1mm, eg. 1.1mm, a standard plate can be selected to fixate that displacement.
Interesting point. I've been wondering how the down grafting is actually performed. Is it some kind of custom fit wedge they put in the gap to get the right angle and down graft amount? In that case it seems like a rather good guide for the displacement. At some point I thought they might just leave the gap and let the bone heal it self, like a normal fracture.