When the OCI image contains a single plugin, which is the most general case, adding the single plugin folder name as a suffix to the OCI reference (after an exclamation mark), like this:

oci://my-quay/my-org/my-repo:tagOrSHA!some-plugin-folder-name

isn't really useful, and generally introduces some duplication since the repo name generally contains a string very similar to the folder name.

When there is only 1 plugin in the OCI image (which can be confirmed in the OCI image index metadata and index.json file), omitting the plugin folder name suffix should be allowed, and this should select the single plugin by default.