I really believe it is a blending of both. When working with someone on wedge shots I want them to be athletic.
What I mean by that is if they were going to throw a ball their arm and body movement would be different for a short throw vs/ a long throw. For a short throw the movement would be small and slower, for a long throw it would be long and faster.
I know it can very from person to person, but I find if you are just talking swing length, like a clock drill, the swing can get to mechanical and have no feel.
By getting someone to be athletic you are helping them understand the correlation between swing length and swing speed. It really is a blending of both concepts.