It also changes what muscles you are exercising. A 100% inclined pushup works your shoulders significantly more than your chest, while a normal pushup exercises

It also changes what muscles you are exercising. A 100% inclined pushup works your shoulders significantly more than your chest, while a normal pushup exercises your chest more. It makes it a completely different exercise altogether — the shoulder press exercise is not a substitute for the bench press and is nowhere near as efficient an exercise to build your chest muscles.