S3 - all the credit to you for testing, but.....If you get the swing sequence right, the wrists serve to transfer and effectively add power. Think tip of a whip or complex pendulum, or a fly line - you can't do anything to increase the terminal velocity after initiation. In the cases of hitting, hammering etc the wrists ALLOW it, rather than MAKE it, to happen.
Having done the experiments and still not buying in, I think you should try to wade through the earlier linked thread with Doc Nathan's explanation of the physics. Yes, it may make your brain muscles hurt, but it is worth it IME.
Best of luck- GM
Yes, I agree 100% that the wrists allow the "power" movement, which is made by the forearm muscles.