... and What is the Correct Domain Account for running SPTIMERV4?
These are two questions that have plagued man for too long. The answers are both 42.
The farm account can't access configure service accounts because it is not in the local administrators group on the server (or at least it is not supposed to be). Thus, it cannot change who runs services. If you want to configure service accounts you must use an account that is in the local administrators (make it yours or maybe the setup account).
The farm account is the correct account for running the SharePoint Timer Service (Windows service). The permissions must get delegated to it by psconfig or some other magical process.
Those are my answers and I'm sticking to them until I get a better answer. I based this on a bit of painstaking research and experimentation. I did not find the correct answer anywhere, but you just found it!
This is based on SP 2010 Foundation on Windows Server 2008R2, but I am pretty sure it holds true for a number of others.