Don't confuse flexibility and looseness. Better balance allows greater freedom of motion. Useful when it's needed, but not always needed if you move efficiently. "Flexibility" to me implies how great your range of motion is in each joint. It's a neuromuscular/structural thing. Looseness is about how free each joint is to move at any moment. Mental/neural/balance thing. If you're moving efficiently, you shouldn't usually have to approach the limits of your range of motion, even if you're not very flexible. Whenever you approach the limit of your range of motion in a particular joint, you begin to run out of potential space for yourself, it's harder to stay loose, and easier for the other guy to feel your structure. Body unity would dictate that you move all your joints a little in a coordinated fashion, rather than moving one or two joints a lot. Make sense?
Don't try to move like anyone else. You can't effectively move like Tim, Al or even like you THINK you should. Develop the principles and observe in a detached way what your body does. No judgement. Gain experience moving with (not against) a variety of people so that you intuitively understand how they move better than they do. Then use that knowledge to nullify anything they could possibly do before the first moment. There is no "you," there is only the other guy's nervous system. It's just movement, it's not personal.
Remember, at the end of the day, there are only a few ABSOLUTES in Guided Chaos: Balance (because of gravity), Looseness (freedom in joints), Body Unity (everything working together) and Sensitivity (subconsciously driven movement), aiming towards maximal efficiency and effectiveness through maximum freedom of action. We train the subconscious through contact flow. Supplemental exercises hasten development and understanding of the principles. Be wary of missing the forest for the trees.
Also be aware that all of the above could be considered a "tree" in the overall forest of GC. Most basic goal is to increase the student's survivability, which depends much more on awareness and mindset than movement efficiency (at least until the day that efficient movement is needed!). Fright reaction, understanding the "interview", and the moral will to strike first and strike decisively and continue until safe escape is assured, are important. Increased sensitivity yields increased awareness and understanding and capability. It's healthier and more fun than going bowling. If you're worried about being attacked, just walk around with a big steel spike in your hand and guns on your belt. . . .