The UID and GID were added when the remote agent updated the /etc/passwd file.
When scanning the file the remote agent would have found that no ID was present in the ID fields, and therefore adds the nobody ID.
Why was that specific UID / GID chosen?
The nobody ID is used as a security measure to limit the access a user can have to the system.
The number given to the nobody UID/GID is Operating System dependant.
As an example: it might be 60001 on Solaris and 65534 on RedHat.
Is this standard best practice?
Yes, at the time when the agent was designed and implemented this was considered best practice.
The CA Agent for NIS/UNIX identifies the userID that has no UID or GID.
The Agent then adds the "nobody" UID and "nobody" GID accordingly. This is done as a security measure to limit the access that a user may have if a user is able to logon locally to the userID with no UID.
The number given to the nobody UID/GID is Operating System dependant; e.g. might be 60001 on Solaris and 65534 on Redhat.