Please help me understand the concept of a 'pre-finisher' in the Jnat world

I think I might already know the answer to this; I want to see if I'm correct.





So on the Jnat sales web sites, some Jnats are labeled as 'pre-finishers'. I assume this means that the stone in question adds some value to the final edge in the honing progression. But do they add anything more than what can be achieved by, say, a full nagura progression on one stone?





The reason I ask is that I'm currently testing a stone which is softer than the other Jnats I have. I did the full nagura progression on it, and came away with a pretty tolerable, but not great shave. So I next put the same razor on a Nakayama Kiita with tomo slurry, and got a very, very nice shave after that.





I think, but I don't know for a fact, that starting on the first stone and finishing on the second gave me a better shave than the nagura progression on the Kiita alone. I have more experimentation to do to prove this to myself, but is kicking up the final edge a notch the hallmark of a pre-finisher, or am I just imagining the results here? I'm still pretty inexperienced, so I want to make sure my assumptions are either right or get corrected.





So, in short, what exactly is a pre-finishing Jnat supposed to do?





Thanks for any insight someone can shed on this for me.