ok, lets look at it this way.
There was a certain level of intelligence, reason and inituition made by the writers and editors of Shadowrun. They wrote the rules in such a way as to give you a generalist view of how or what a limb (or the matrix, or magic, or purple-people-eaters) can do. From there, it is up to the group of players/GM to decide what task is reliant what part of a limb or given limbs. In effect, the Writers and editors said "we are going to assume our readers are *this* smart" <wave hand in air>. The book ended up being 500 freaking pages long! How much larger, or how many volumes would it be if they assumed their customers were morons?
AS with any game that is powered by imagination, sometimes you have to use it to come to an appropriate ruling on a given device, ritual, spell, code, or ware. Come up with that ruling, remember it, and apply it evenly across the board and move on. Rules are there to guide the game, they are not the game in and of itself.