If you don't actively open the wrist, then you're not getting as much out of your wrist. Its really that simple. Timing is essential, you should resist the wrist breaking closed going into the hit (of course it will wag slightly back), and when it starts to bounce back forward you then actively open it. But it has to be done at the right timing to work properly.
Also, you can't get tendon bounce unless you apply force to the wrist (either to keep it in place, or to actively open it). And tendon bounce isn't a hypothetical thing, it is real, and you can see it for yourself. Whenever somebody tries to keep a limb held motionless, and somebody else (or something) bumps into it, there is a natural "springiness" or tendency to rebound, or bounce back into the position in which it is being held. This is because your muscles and tendons are elastic, they are not rigid. If they were rigid, then you'd damage and eventually break your bones at the joints every time you jump or run or do anything with sudden jerky motions. Nature saves us from this latter fate by making us elastic.
What previous descriptions of tendon bounce and its role in throwing have failed to do is to also consider the dynamics of rebound. You see, the rebound of tendon bounce occurs on the "rebound time scale" (the time it takes for the disturbed limb to bounce back in place). The rebound time scale changes from person to person depending upon wrist strength and muscle fiber, tendon structure, and conditioning. You can also change it yourself by holding more firm or more loose. People who work with their hands a lot, pounding hammers, painting walls with huge paint brushes, etc., will develop more well-conditioned tendons and muscle structure, and their wrists will be more springy. If you put a disc in your hand, then the rebound time scale will be significantly longer than without it, because the disc adds inertia to the motion.
There is a large body of physics on stuff like this. The time scale in all sorts of phenomena where there is a restoring force that bounces things back into place is always something like the square root of mass
m divided by a spring constant
k. You can write this as
t~sqrt(
m/k). The implication is that the time scale for rebound also depends on the weight of your disc, although the dependence is weak and differences like 165g vs 175g will not mean very much. The spring constant
k is the amount of force your wrist makes in the open direction when it is forced closed. You can change your effective value of
k by going from holding your wrist neutral and then actively opening it. Since
k is then increasing as you force the disc in the motion as your wrist opens, the time scale is also decreasing as the wrist opens. That means that the disc is accelerating forward, owing to the increasing force applied by your wrist.
You can measure your own rebound time scale. You should measure your own rebound time scale. Or at least do this exercise to get the feeling for what the time scale is, and how it changes with the amount of force you apply. Put the disc in your hand with your usual grip, and hold your wrist firm at the neutral position. Tuck your throwing elbow into your side, to help keep your arm rigidly in place. With your other hand, grasp your wrist and hold it in place. Try to make your throwing arm up to the base of your wrist as rigidly held as possible so that the rebound of other parts of your arm and body do not pollute the results. Now, holding the disc plane horizontal, have somebody else perturb the nose of the disc in the closed wrist direction (like a quick little hammer strike), and watch it bounce back (or you can bump it against something else to get the same effective result). If you are holding your wrist firmly in place, after being displaced it will wag back to neutral and will also slightly oscillate until it comes to rest.
Now that you've read this far, its time to reveal my latest thoughts on big snap and something called "resonance." Resonance occurs when a system (in this case, your wrist, hand, and disc) is forced at the same period (i.e., time scale for rebound) as the natural rebound period (i.e., the rebound time scale). It is a very powerful phenomenon, and I think that it is the only thing that can explain why some players can throw so damn far.
Wikipedia has a decent quick description:
http://en.wikipedia.org/wiki/Resonance which is OK for now. Think about the pushing the swing analogy, it is closest to the scenario of wrist wagging back and forth.
Your goal, if you want to get more out of your wrist action, will be to take the disc through the hit portion of your throw on the same time scale as the wrist rebound time scale. That is at least half-hitting it. Play with your mechanics, your pull speed, etc., until you get resonance into your throwing motion. To get a full hit, you'll have to apply the correct leverage and increasing strength going into the release as you also increase the force applied to actively opening the wrist. This is far more tricky.
Anyways, enough of this for now...busy watching an old man beat up on the Patriots.