Generalized shapes might help if you're drawing extremely regular objects (books, balls, apartment buildings) or perhaps if you need to draw a generic "horse" from memory but it's not a big help with life drawing. Edwards and other life drawing teachers often suggest drawing the negative spaces as a way of breaking the habit of using the brain to figure out what the object is "like" (e.g. it's like a square sitting on a circle) and focus on what it is.