Reading a bit tonight threw up a perspective which may help explain some of the positive results people report from stropping - even though the grit/particle sizes may not at first look be that much different.
Grinding and to a fair degree honing seem essentially to be abrasive cutting processes where each grit acts like a cutting tool and removes material from the in our case blade by gouging out a groove. The result is a fairly heavily scored surface - a network of criss crossing scratches running in whatever direction the blade was moving on the stone.
Superfinishing is interesting. It's widely used on engineered parts where low friction and wear in use are very important - stuff like precision gears, car steering parts etc. It's realised in multiple forms depending on the shape of the parts to be processed (try Googling 'superfinishing' and also YouTube - it brings up all sorts of diverse links), and to a degree involves using an abrasive, but with a very fine grit indeed - or in fact materials/media which are not necessarily very abrasive at all. e.g. steel beads and all sorts of things. Movements tend to be short and multi directional, and to result in a highly polished or if less fine slightly hazy surface.
The key point seems to be that superfinishing like this takes the scratched/gouged surface produced by cutting grits in grinding and honing, and by rubbing or burnishing the surface rather than cutting knocks the peaks off the ridges - and possibly also moves a micron thin surface layer about to smooth things out even further. It can reduce the CLA/RA reading by a factor of up to 10 it seems. Guessing, but there could very well be work hardening going on too.
It's also offered for use on parts like the disc type knives used to slit sheet and film materials in many continuously strip fed industrial processes - and (in one example anyway) is claimed to greatly reduce web friction, and to extend life between re-sharpenings by a factor of four or five. One factor mentioned in this is straightening and/or removal of any wire edge.
Lapping may be somewhere on the overlap - perhaps depending to quite a degree on the nature of the abrasive used. e.g. very hard gits like diamonds may cut/scratch more than some of the more traditional compounds that break down quite a lot. Reading about stropping and burnishing compounds there seem to be quite a few about that break down like this.
Maybe this relative softness/friability is an important part of how they work. (the emphasis becomes burnishing/rubbing rather than any cutting action/removal of metal) Maybe it's one of the reasons why stropping with the right compound delivers better results than the basic grit size information might suggest. Might explain too some of why a leather or dry MDF lap (with no abrasive) may do a good job, and why a fine waterstone using e.g. a nagura to produce a slurry that beaks down may give a very hard wearing and free cutting edge compared to another of nominally the same size but much harder grit.
Here's a thought. It seems that lots of low amplitude multi directional movement helps with superfinishing. (it would presumably tend to increase the amount of burnishing/rubbing going on) Wonder if anybody has ever tried using a vibrating platform on which to mount very fine grade waterstones or other very fine sharpening media while using it?
ian