Tested in vB4.0.2 PL4 - the hack itself works and displays:
Redirecting...
You have selected a banned timezone!
But this optional setting in ACP doesn't work...
Redirect User?
Enter the URL of which a user should be redirected to if they choose a banned timezone. Leave blank to display error page.
It merely gets ignored, at least that's what I've found under test conditions.
Hope this helps