Jenkins has many custom folder types that extend from AbstractFolder rather than folder.

Where it makes sense the config-file-provider should support these files also.

e.g.

jenkins.branch.OrganizationFolder
org.jenkinsci.plugins.workflow.multibranch.WorkflowMultiBranchProject (whose parent is not an organisationFolder - this is already taken care of in the ACL)

Generally I think this can be simplified to be any AbstractFolder that is not an descendant of a ComputedFolder, which in turn can be simplied to any AbstractFolder that can be configured.