As long as we are splitting hairs... Yes NT 4.0 Domain Controllers do have a local Administrator account and password, it just so happens to be the same account that the BDCs use as well because on NT 4.0 Domains the PDC is the only controller that maintains an authoritave SAM.

Any password changes are actually passed onto the PDC, the BDC has a copy of that file.

It can be modified just like any other account.