So, you don't think doing front squats will develop your legs differently than doing back squats?
Leg extensions are a quad exercise. Will your quads develop differently doing leg extensions vs. doing squats?
Will tricep cable pushdowns develop the triceps the same as tricep French presses?
As a clarification, I do want to distinguish between muscle groups that have various functions such as the shoulder. Doing just front delt movements at the expense of rear delt movements will result in an unbalance overall shoulder development. Front delts will develop and the rears will remain pretty much the same. Same with traps. If you are just doing shrugs you will develop your "upper traps" but it won't have nearly the affect on your lower, midback portion of the trap as evidence with Mentzer.
But if you do squats exclusively or hacks exclusively it will have a different effect on your body as the squats also include a lot of lower back and glute action. So though this might effect the degree to which your quads respond and grow, the actually look, disregarding any size discrepancy, will remain the same. Exactly the same. You won't get more upper, lower, outer, inner development doing one or the other. The shape of your quads as it grows will be entirely dependant on it's genetic predisposition.
Like Brignole said, "Try it". Try do just squats for six months and then do hacks for six months. The only difference you will experience, if any, is with the size of the muscle. The actual shape and how it developed will go unchanged. Do any variation of tricep or biceps movements and see if it makes one iota of a difference in the shape of your muscle.
Dorian, when training that guy who does those "London Real" videos remarked, somewhat sarcastically how silly he thought it was that you could develop your inner or outer calf depending on toe position. As if your outer calf just suddenly shuts off because you point your toes out. Even if pointing your toes out feels like it is putting more stress on your inner calf it is trivial. Your whole calf is contracting no mater what angle your toes are.