Well if your looking for a reason to buy the coticule its the same as saying a $180 TI will give as good a shave as one of the maestro's so why spend almost $1000 for it?
I have both the norton and the yellow and blue coticule. At this point in my life I use the Norton 4K and then the yellow coticule. I find the blue coticule works very slowly while the yellow imparts a finer edge than the Norton 8K.But is that a reason enough to spend the money. I don't think so. For me I just like using the natural stone. I don't think the increased longevity of the coticule in and of itself is worth the difference either.
You know its just one of those things where you spend your money where you want.
As to using kerosene on the stones that is probably for lubrication purposes. In my college days I used to work in the geology lab grinding, polishing and cutting rocks. Our lap saw with the diamond blade used kerosene as both lube and coolant for the blade. it increased its longevity which is why the commercial operations probably use it with straights in the grinding and honing process.