The example response contains a Parameters resource, but it is not a valid Parameters resource.  If the return had multiple bundles, then a Parameters resource is used and the Bundle is placed in Parameters.parameter.resource.  If there is a single Bundle returned (as in this example), then no Parameters resource used in accordance with  http://hl7.org/fhir/2022Sep/operations.html#response (If there is only one out parameter, which is a single Resource with the parameter name "return" then the parameter format is not used, and the response is simply the resource itself. ) It is unclear if "which is a single resource" means that the cardinality is 0..1 or 1..1, and if 0..* returning only one instance is allowed to not use Parameters in the return.