Unfortunately that overwhelming belief is also mistaken.
Using weights doesnt always mean isolation. The best example is the Dead Lift. This is where you have a massive weight, and just lift (using your legs of course, not you back) to just above knee height. This exercise builds up what is called core muscles and core strength. Legs, arms, back are all worked out. Bone structures are strengthened, as well as joints.
This is just one of many exercises that are "complete body".
But ur single greatest misconception is that muscles work in tandem with each other. Take for example your arms. Each muscle is independent from each other (you do have opposing groups - biceps/triceps for example but they are still independent), thats why you see sometimes people with massive biceps, and no triceps.
Other groups, like abdominals/intercostals... or ur trunk, have muscles are are connected, but still independent.
Another point where you are being misled, is the fact that because you are able to use more muscles, you can do more intense workouts. What you are doing is utilising large amounts of muscle groups, instead of focusing on specific areas.
The simple fact is this. If you are just starting to lift weights, or bodybuild, you need to do alot of core exercises. Some examples are -
Squats, Deadlifts, Clean and Jerks, Military or Push Presses, Chin Ups etc. All these exercises build large areas of muscles, and provide a solid foundation for more specific training later on.
The biggest problem I have with your method, is the fact it is very violent, and quite dangerous. Movements that are that sudden and jerky, promote damage to delicate parts of your body... particiularly the lower back. Swinging a large heavy mass around is the reason people throw their backs out. Damage to joints and tendons wouldnt be surprising.
I strongly suggest you stop doing those kinds of exersises. If you want to get strong, Kalisthenics. It wont be long before you cause damage to yourself.
Your a very educated person, and i strongly suggest you research a bit more regarding this.... particularly because it pertains to your health.