Well, to be fair..
Wouldn't FS Nose Grind, FS Overcrooks just be the side of the rail you approach?
It may not look like much of a change once you're in the grind but
I would imagine it's more difficult to approach the other side of the rail
and tweak the other way if you're unfamiliar.
Thus labeling them front side, back side?
Also, Not entirely sure but I'm using what I know and trying to learn here aswell but
I think that's how you get the term fs bs blunt, etc.
Approach frontside, turn back side blunt.