Why Account:rename administrator account works only on Domain Security Policy and doesn't work on any manually created group policy and Domain Controller Security Policy?

I try to deploy Account:rename administrator account group policy to any client computer joined to domain controller in windows server 2003, However the policy seem to works only on Domain Security Policy.

This is what I did:

Open Active Directory Users and Computers,created an organizational Units folder and manually created a new group policy in the group policy tab or add Domain Controller Security Policy, and rename the default administrator account name to any other name in Account:rename administrator account and gupdate /force in the client computer and it doesn't work.

But when I tried to set the same policy in the Active Directory Users and Computers,created an organizational Units folder and addDomain Security Policy  in the group policy tab it works fine.

Can someone explain me why it works only in Domain Security Policy?

Regard,

Thanks.