A commonly miss-understood capability of the vSphere Content Library is managing and distributing Virtual Machine Templates (VMTX), which was introduced in vSphere 6.7 Update 2.
When vSphere Content Library was first released in vSphere 5.0, content was distributed by using a pull-based replication where the subscriber vCenter Server would setup initiate the content subscription to the publisher vCenter Server and then content would then be downloaded to the subscriber vCenter Server as shown in the diagram below.
This initial architecture of vSphere Content Library made it extremely easy for any vCenter Server, regardless of their vCenter Single Sign-On domain, to create a subscription and download content (ISO, OVF/OVA and other files) from the vSphere Content Library of the publisher vCenter Server.
The creation of the vSphere Content Library subscription was managed completely by the individual subscribing vCenter Server as long as it knew the subscription URL and any credentials that may have been configured and of course connectivity to the publisher vCenter Server. While this made it easy for anyone to subscribe content from a vSphere Content Library, it also meant for larger organizations with many vCenter Server(s), an additional task was required to configure each subscribing vCenter Server.