The person is also referred to as an "agent" or "authorized signer" depending on state law or contract language. In essence, the person can sign on the account, but has no ownership interest in the funds or survivorship interest if the owner dies. It's analagous to a power of attorney over a particular account at a particular bank.
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In this world you must be oh so smart or oh so pleasant. Well, for years I was smart. I recommend pleasant.