I am referring to this post: http://geekswithblogs.net/evega/archive/2004/10/13/12594.aspx
Basically the first application pool settings it is asking for it the administrative one and the seconds is for the extended virtual server.
The first one needs to have access to SQL but the second does not as “the administration virtual server account will create any databases required“. Quote found from Remote SQL Server Deployment of WSS
So use two different account with access described as above.