I’m trying to consider cases of using derived unhardened child keys. My understanding is that this type of key within a tree can be created without the master extended private key i.e. can be created with a child extended public key. I also see that the extended public key could cause security issues to the HD tree at large should another child private key be exposed as well (master extended private key not compromised in this scenario).
Regardless of specific use-case, is the owner of unhardened child keys trying to publicly display a relationship?
If for something more simple like internal organization, what advantage does a sub-tree of an extended public key provide over assigning roles to hardened child keys?