In Kusanku Sai kata, which I learned from Charles Murray, there is a movement where a single sai is thrown into the floor, and then a third sai is pulled from your obi on your back, to continue on with the kata.
Kusanku Sai kata, was created by Shimabuku Tatsuo, his using Kusanku kata as the basic template for the kata, and then he incorporated a section from an earlier kata he had created, Kyan No Sai, to complete the form.
After the throw a 3rd sai , which was already held in the obi on the back, is extracted and the form continues. Often today the kata is done with two sai and the throw is only simulated, then the form continues.
What Sherman told me during a clinic he was conducting in Chicopee, Mass. Was that when he originally learned the form, the sai thrown was not into the floor, rather it was to be thrown into the torso of the opponent, a change that is quite different.
Then as the dojo got more crowded, the intent of the throw was changed, then a throw into the ground, for safety reasons. It would not be prudent to have anyone throw the sai into another students body.
At that point the intent of the throw was changed.
Now realistically there is plenty of reason not to attempt to change this throw purpose back to the original. For one reason rationally we are not going to be throwing sai into anyone anytime soon. The nature of society has changed.
Also when Charles was in Okinawa, he visited a Goju dojo where the students were throwing their sai into a tree before class. There are many types of different sai on Okinawa, some quite light and dagger like. Here is a photo of Matayoshi Sensei doing the same tree throw.
This was the video which I used to make the screen shots.