This lecture in the first table explains the effect of the sticky bit as follows:

"Users with write access to the directory can remove only files that they own; they cannot remove or force saves to files that other users own."

A more correct definition would look like the following:
"Users, even if they have write permissions to the directory, cannot delete or rename files that they don't own." (The owning user of the directory and root can delete all files of course)
That's it. I don't know what the original sentence meant by "force save". The ability to modify a file has to do entirely with the permissions on the file itself. The sticky on the directory doesn't affect that.

Also, the same lecture has the following example that needs to be improved or removed:

Remove the setuid bit on the example directory by using the symbolic method:

user@host:~$

chmod u-s example
The SUID bit has nothing to do with directories. It is for binary executables. Use another example. But generally, you don't want to remove SUID from a program and break functionality as a result.