It all depends on how you look at it. If I turn just the center slice without turning the two sides, it's just one move. That's no different than an R turn. If you turn the right layer and the other two layers don't move, it's just one one move. But by the logic employed in making a center slice turn count as two moves even if the other two slices don't move is no different than counting a right turn as two moves even if the other two slices don't move. I can't really see the difference. If that's the case, why not then consider a cube turn as three moves? After all, all three slices are turning. It's all perspective.They should absolutely not. A slice move is turning 2 layers a once just like a r is really turning L x. Just because M' is one motion does not men it's one move. (I get that r isn't a perfect example because rotations don't count as move but the point was you're just combing multiple thing into one turn.)