No disagreement here.... its just that using the Welcome Screen is a tad more "immediate".
If the mutator(s) were unloaded/removed then I would most certainly remove the notice. I say this after a 28 hour test to see if there are any trubs with keeping the two muts up and running reliably. They are reliable.
A mutator sometimes can get unloaded on a map change if there is a mistake in the configuration of a server. As an admin, you won't get a message if that happens, meaning you will be too late to remove any message from the welcome screen.