>>59052557I think it's a relatively non-specific attack, that just, as it states, stabs or slices a target with sharp stones.
If the pokemon has a body part that can be used for this, it uses it.
If it can't, it's employing the earth controlling abilities responsible for moves like Earthquake and Rock Slide to form a spike of stone and use that.
Kind of like how moves like Horn Drill can use a wide variety of stabby bits, not just "horns" Stone Edge is a very pragmatic move, not so much a prescriptive one.
