The animation doesn't actually change according to the minimize-speed-threshold. Even when you change its value from 100 to 0, the animation is still normal like what you encountered, @Nirmik. What I observe though is that if the minimize-speed-threshold is set to 100 (which is the default), and the minimize-count is set to 0 (also the default), the animation is slow just like when we first run 12.10 after upgrading/installing it.
Now, the animation will actually get faster every time you minimize a window, since the minimize-count will increase, and the larger it is the faster the animation. The increase in value of minimize-count will stop up to the value of the minimize-speed-threshold.
If you click on the minimize-count, you will see a description that says:
This is used to adjust the animation speed by making it progressively faster the more it is used.
For Slow Animation, I suggest to set up the following:
minimize-count = 0
minimize-fast-duration = 1000
minimize-slow-duration = 1000
minimize-speed-threshold = 0
For Faster Animation, I suggest to lower down the value of minimize-fast-duration and the minimize-slow-duration.