In a distributed file system with mutual authentication, access control must be enforced across multiple nodes and networks, so it cannot rely solely on a single host's OS; instead, it depends on distributed authentication and authorization mechanisms (such as certificates, tokens, or directory services). At the same time, because data travels over the network, eavesdropping is a real risk, so encryption and mutual authentication are used to protect confidentiality and prevent man-in- the-middle attacks.
In contrast, in a multi-user host, access control can usually be managed directly by the local OS (file permissions, user groups, etc.), and eavesdropping is less of a concern if the host is physically and logically isolated.