Security concern and a bit confused

I stumbled upon this Group policy setting that when I Disable the policy, the Admin Username will not be displayed in the UAC prompt when elevated from a Standard user account.
Enumerate administrator accounts on elevation

Meanwhile, I can select and see the Admin account username on the Sign-in screen...

This policy setting is useless then. Please correct me if I am missing something.

The policy states it only hides the administrator name from the drop down list for runas

Well, I have it as Not Configured.
How important is this policy from a security standpoint for a standalone machine?
Do I really need to hide the Admin username on the UAC prompt?

The Username can be shown anyways on the sign-in screen. both for Standard and Admin accounts.

However, my password is long and complex.

Its a bit pointless if you can see the name at login

I will just leave the Group Policy setting as default meaning Not Configured.