Why set a DDboost passphrase when upgrading AVE?

In the avamar AVE upgrading documentation ( https://www.delltechnologies.com/asset/en-us/products/data-protection/technical-support/docu91853.pdf pg.111) it is specified that if the AVE is interfacing with a DD system, via a DDboost account, you must "enable a passphrase for the DD Boost user" on the DD system.

Verbatim:

Set a passphrase on the Data Domain systems
     When you upgrade an AVE that is connected to a Data Domain system, enable a
     passphrase for the DD Boost user by performing the following steps:
            (Note: The DD Boost user must have admin rights.)
                   Procedure
                        1. Log in to the Data Domain system.
                        2. Type the following command at the Data Domain CLI: system passphrase set
                        3. When prompted, type a passphrase

First of all, the wording is confusing to me. Isn't a data domains passphrase system wide? 

Also is it not basically required that a passphrase be set already, or is this just saying that it needs to be reset to a different one upon avamar AVE updating, if so why?