"SYSTEM" is not an account. It is a SID, a role, an account type. And that SID, by itself, doesn't work for most network tasks, so whatever account they are using must also include a SID that does have network privileges.
There probably is a good reason why it needs a privilege in Windows which doesn't exist in Linux. It could be anything, and it might not even be a privilege associated with the SYSTEM role: it might be a privilege associated with the other role.