Clarify the notion and mechanisms for server-managed information

What are the conceptual and implementation differences between server-managed containment triples and the triples in server-managed resources (auxiliary)?

It appears to be that we have two different mechanisms in the spec that are conceptually similar, if not the same. How can we reconcile this?

Containers are self-descriptive in that the containment information is part of the resource description and managed by the server. Contained resources are tied to the lifecycle of the container. Container may include other information provided by clients. Containment triples can't be updated by clients.

Server-managed resources (auxiliary) are independent resources discovered through primary resources and are tied to their lifecycle. Server-managed resources are not writeable by clients.

We can see that although cumbersome, containment information can be found in a server-managed resource (auxiliary). We can also see that any information that can part of a server-managed resource (auxiliary) can instead be in a self-descriptive resource.