It shouldn't do anything. Setuid scripts have been disabled in the kernel - the executable pointed to by the script would have to be setuid.
Scripts are impossible to write securely. There are too many paths for untrusted data to enter and cause major security problems.
And the "race condition" mentioned in that reference cannot be avoided. The problem is that "testing" the scripts permissions is done first, then the interpreter is started to run that script. Unfortunately for setuid scripts, the script itself can be replaced between the time the test is done, and the time the interpreter opens the script for interpretation. This doesn't happen for binary executables as the file is not closed between the test and loading of the file.