Cloning currently only link all parameters. Maintaining a clone state of the internal node-graph is quite challenging: Nodes must be created, deleted and modified on the fly, as well as their expression (links) to their actual parameters on the Group interface.
The whole process of making sure the clone is up-to-date, would probably be exactly the same as copy/paste the Group itself and then link the Group parameters to the original node. It's not something that you probably want to do as many time as any edit is done in the original Group node.
Maybe a button could exist, such as "Refresh clones", or rather a warning indicating that they are no longer synchronised or even a total removal of the clone links with user permission.